2492 + Interview Questions in CURRENT-ELECTRICITY IN GENERAL AWARENESS Page 30 InterviewSolution

1451.	The direction of current density is ……. To the direction of friff velocity of electrons in the conductor
Answer» Correct Answer - opposite

Discussion

1452.	A Steady current flows in a metalic conductor of non uniform cross section. The quantity/quantities which remain constant along the length of the conductor is/areA. Current,electric field and drift speedB. drift speed onlyC. current and drift speedD. current only
Answer» Correct Answer - D

Discussion

1453.	In a closed loop when current has not been reached the stedy start , the current through different cross-section of the irregular shaped conductor of a particular instant would have……… values.
Answer» Correct Answer - different

Discussion

1454.	A metallic conductor of irregular corss-section is as shown in the figure. A constant potential difference is applied across the ends `(1)` and `(2)`. Then: A. the current at the cross-section `P`equals the current at the cross-section `Q`B. the electric field intensity at `P` is less than that at `Q`C. the rate of heat generated per unit time at `Q` is generated than that at `P`D. the number of electrons crossing per unit area of cross-section at `P` is less than at `Q`
Answer» Correct Answer - A::B::C::D `(A) I_(P)=I_(Q)` `(B)J=sigmaE` `J_(P)ltJ_(Q)` `E_(P)ltE_(Q)` (C) `H=I^(2)R & R prop 1/A` `R_(P)ltR_(Q)` `H_(P)ltH_(Q)` (D) For metal `n` is independent of temperature

Discussion

1455.	In the circuit shown in fig. the capacitor is initially uncharged. Two way switch `(s)` is placed in position 1 for a very short interval of time `(Delta t)` and then is moved to position 2. The switch is held in position 2 for equally short interval `Delta t` and is then moved back to position 1. The process is repeated a large number of times until the charge on the capacitor stops changing. find this final a value of charge on the capacitor. [Assume that in each contact the charge on the capacitor changes by a very small amount]
Answer» Correct Answer - `7 muF`

Discussion

1456.	In the Fig. two neutral spherical conductors of radii `2a and a` are separated by a large distance. Initially, switch `S_(1)` is kept closed and `S_(2)` is open. Now `S_(1)` is opened and `S_(2)` is closed at `t = 0`. (a) Find the rate of fall in potential of the conductor of radius 2a as a function of time. (b) find the heat dissipated after `S_(2)` is closed.
Answer» Correct Answer - (a) `(V)/((8pi in_(0)a)R)e^((-3t)/(8 pi in_(0)aR))` (b) `(4pi in_(0)aV^(2))/(3)`

Discussion

1457.	A charged capacitor `(C_(1) = 3 mu F)` is getting discharged in the circuit shown. When the current `I` was observed to be 2.5 A, switch ‘S’ was opened. Determine the amount of heat that will be liberated in the circuit after ‘S’ is opened.
Answer» Correct Answer - `121.87 muJ`

Discussion

1458.	In the circuit elements given below, all individual resistors are identical. The resistance between P and Q in the different cases is A. a) `3R`B. b) `5R//6`C. c) `R//2`D. d) R
Answer» Correct Answer - b,c,d Here the resistance are is parallel their effective resistance is `R//3` Hence answer is wrong (b) The effective resistance of first three resistance in parallel in `R//3` and next two resistance in parallel is `R//2`. Therefore the total resistance `= (R//3) + (R//2) = 5R//6` (c) The upper tweo resistance and lower two resistance are in series .The effective resistance of each arm `= 2R` These two effective resistance `= (2R xx 2R)/(2R + 2R) = R`. Now these two arms of resistance is in parallel with resistance `R` Hence effective resistance `P` and `Q` `= (R xx R)/(R + R) = (R )/(2)` (d) By symmtery the mid-joined `R` would not carry any current so effective resistance is only for `2R and 2R` parallel which will be `R`

Discussion

1459.	Which of the following quantities do not change when a resistor connected to a battery is heated due to the current?A. drift speedB. resistivityC. resistanceD. number of free electrons
Answer» Correct Answer - D

Discussion

1460.	A current passes through a wire of nonuniform cross-section. Which of the following quantites are independent of the cross section?A. the charge crossing in a given time internalB. drift speedC. current densityD. free-electron density.
Answer» Correct Answer - A::D

Discussion

1461.	A current passes through a wire of nonuniform cross-section. Which of the following quantites are independent of the cross section?A. free electron densityB. current densityC. drift speedD. the charge crossing in a given time internal
Answer» Correct Answer - a,d When current passes through a wire of none-uniform cross-section, there of the wire. It means, the charge crossing is a given time interval over every cross-section of wire. The no of free electrons per unit volume i.e. free electron densidy is also independent of the cross-section of the wire

Discussion

1462.	A current passes through a wire of nonuniform cross-section. Which of the following quantites are independent of the cross section?A. the charge crossing in a given time inverval.B. drift speedC. current densityD. free-electron density
Answer» Correct Answer - A::D

Discussion

1463.	A current passes through a wire of nonuniform cross-section. Which of the following quantites are independent of the cross section?A. independent of area of cross-sectionB. directly proportional to the length of the conductorC. directly proportional to the area of cross section.D. inversely proportional to the area of the conductor.
Answer» Correct Answer - A

Discussion

1464.	Drift velocity `v_(d)` varies with the intensity of electric field as per their relationA. `v_(d)alphaE`B. `v_(d)alphaE^(2)`C. `v_(d)alphasqrt(E)`D. `v_(d)=` constant
Answer» Correct Answer - A

Discussion

1465.	Drift velocity `v_(d)` varies with the intensity of electric field as per their relationA. `v_(d)propE`B. `v_(d)prop(1)/(E)`C. `v_(d)="constant"`D. `v_(d)propE^(2)`
Answer» Correct Answer - A

Discussion

1466.	An electric wire of length ‘ I ’ and area of cross-section a has a resistance R ohm s. Another wire of the same material having same length and area of cross-section 4a has a resistance ofA. `4R`B. `R//4`C. `R//16`D. `16R`
Answer» Correct Answer - B

Discussion

1467.	If n, e, `tau`, m, are representing electron density charge, relaxation time and mass of an electron respectively then the resistance of wire of length 1 and cross sectional area A is given byA. `(ml)/("ne"^(2)tauA)`B. `(mtauA)/("ne"^(2)l)`C. `("ne"^(2)tauA)/(ml)`D. `("ne"^(2)A)/(ml)`
Answer» Correct Answer - B

Discussion

1468.	For which of the following the resistance decreases on increasing the temperatureA. CopperB. TungstenC. GermaniumD. Aluminium
Answer» Correct Answer - C

Discussion

1469.	If n, e, `tau`, m, are representing electron density charge, relaxation time and mass of an electron respectively then the resistance of wire of length 1 and cross sectional area A is given byA. `(ml)/(n e^(2)tauA)`B. `(m tau^(2)A)/(n e^(2)l)`C. `(n e^(2) tauA)/(2ml)`D. `(n e^(2)A)/(2mtaul)`
Answer» Correct Answer - A

Discussion

1470.	The relaxation time in conductorsA. Increases with the increase of temperatureB. Decreases with the increase of temperatureC. It does not depend on temperatureD. All of sudden changes at 400 K
Answer» Correct Answer - B

Discussion

1471.	The relaxation time in conductorsA. Increase with the increase of temperatureB. Decrease with the increase of temperatureC. It does not depent on temperatureD. All of sudden changes at `400 K`
Answer» Correct Answer - B (b) Because as temperature increases, the resistivity increases and hence the relaxation time decrease for conductor `(tau prop (1)/(rho))`

Discussion

1472.	Drift velocity `v_(d)` varies with the intensity of electric field as per the relationA. `v_(d) prop E`B. `v_(d) prop (1)/(E)`C. `v_(d) =` constantD. `v_(d) prop E^(2)`
Answer» Correct Answer - A (a) `v_(d) = (e)/(m) xx (V)/(l) tau` or `v_(d) = (e)/(m). (El)/(l) tau` (Since `V = El`) `:. V_(d) prop E`

Discussion

1473.	Find the potential difference across each of the four batteries `B_1, B_2, B_3` and `B_4` as shown in the figure.
Answer» Across `B_1` This battery does not make any closed circuit `:. i=0` or `V=E=4 "volt"` Across `B_2` This battery is short circuited. Therefore `V=0` Across `B_3` and `B_4` A current in anti clockwise direction flows in the closed loop `abcda`. This current is `i=("net emf")/("net resistance")=(10-5)/(1+2+2)` =1A Now, current flows through `B_3` in normal direction. Hence, `V=E-ir=10-1xx1=9 "volt"` From `B_2` current flows is opposite direction.Hence, `V=E+ir=5+1xx2=7 "volt"`

Discussion

1474.	1 ampere current is equivalent toA. `6.25xx10^(-18)"electrons s"^(-1)`B. `2.25xx10^(-18)A"electrons s"^(-1)`C. `6.25xx10^(14)"electrons s"^(-1)`D. `2.25xx10^(14)"electrons s"^(-1)`
Answer» Correct Answer - A `Q=It "also" Q="ne" [e=1.6xx10^(-19)C]` `therefore =It or n=(It)/(e)=(1Axx1s)/(1.6xx10^(-19))` `6.25xx10^(8)"electrons s"^(-1)`

Discussion

1475.	A current in a wire is given by the equation, . `I=2t^(2)-3t+1`, the charge through cross section of : wire in time interval t=3s to t=5s isA. 32.33CB. 43.34CC. 45.5CD. 42C
Answer» Correct Answer - B As `i=(dQ)/(dt), dQ=(2t^(2)-3t+1)dt` `int dQ=underset(t=3)overset(t=5)(int)(2t^(2)-3t+1)dt,Q=[(2t^(3))/(3)-(3t^(2))/(2)+t]_(3)^(5)` `=[(2)/(3)(125-27)-(3)/(2)(25-9)+2]=43.34C`

Discussion

1476.	It was found that resistance of a cylindrical specimen of a wire does not change with small change in temperature. If its temperature coefficient of resistivity is `alpha_(R)` then find its thermal expansion coefficient `(alpha)`.
Answer» Correct Answer - `alpha=alpha_(R)`

Discussion

1477.	A bulb B is connected to a source having constant emf and some internal resistance. A variable resistance R is connected in parallel to the bulb. If the resistance R is increased, how will it affect the- (a) Brightness of the bulb? (b) Power spent by the source ?
Answer» Correct Answer - (a) Increases (b) decreases

Discussion

1478.	A cylindrical conductor is made so that its resistance is independent of temperature. It is done by stacking layers of copper, carbon and nichrome as shown in figure. The length of each copper layer is 1 cm and sum of lengths of consecutive carbon and Nichrome Leyers is also 1 cm. find the length of each Nichrome segment. Given [`rho =` resistivity, `alpha =` temperature coefficient of resistivity] `rho_(Cu) =1.7xx10^(-8) Omegam^(-1) ,rho_(C)=5xx10^(-5)Omegam^(-1)` `rho_(Ni) =1xx10^(-6) Omegam^(-1) , alpha_(Cu)=3.9 xx 10^(-3) .^(@)C^(-1)` `alpha_(C)=-5xx10^(-4) .^(@)C^(-1), alpha_(Ni)=4xx10^(-4) .^(@)C^(-1)` Assume no change in dimensions of the segment due to temperature change.
Answer» Correct Answer - 0.98 cm

Discussion

1479.	The length of a potentiometer wire is `l`. A cell of emf `E` is balanced at a length l/3 from the positive end of the wire. If the length of the wire is increased by l/2. At what distance will the same cell give a balance point.A. `(2l)/(3)`B. `(l)/(2)`C. `(l)/(6)`D. `(4l)/(3)`
Answer» Correct Answer - B

Discussion

1480.	An electron revolves in a circule at the rate of `10^(19)` rounds per second. The rquivlent current is `(e=1.6xx10^(-19)C)`A. `1.0 A`B. `1.6A`C. `2.0A`D. `2.6A`
Answer» Correct Answer - B

Discussion

1481.	A cylindrical copper conductor AB length `L` areaa of cross-section a has large number of free electrons which at mean temperature move at random within the body of the conductor like the molecules of a gas. The average thermal motion at room temperature is of the enter of `10^(5)ms^(-1)` where a potential difference `V` is applied free electronic in the condictior experience , the free electrons in the conductor experience force and are accelerated towards the positive emf of the condutor on their gained kinetic energy After each collision the free electronic are angle acceleration due of the electric field , towards the positive end the conductor and next collision with the ions/atoms of the electrons The average speed of the free electrons with which they drift toward the positive and of the conductor under the effect of applied electric field is called drift of the electrons The drift speed of the electrons depends onA. dimension of the conductorB. number density of free electrons in the conductorC. both (a) and (b)D. none of these above
Answer» Correct Answer - d The driff speed of the electron `V_(d) = (eE)/(m) tau` Which is independent of demensions and number density of free electrons in the conductor.

Discussion

1482.	A cylindrical copper conductor AB length `L` areaa of cross-section a has large number of free electrons which at mean temperature move at random within the body of the conductor like the molecules of a gas. The average thermal motion at room temperature is of the enter of `10^(5)ms^(-1)` where a potential difference `V` is applied free electronic in the condictior experience , the free electrons in the conductor experience force and are accelerated towards the positive emf of the condutor on their gained kinetic energy After each collision the free electronic are angle acceleration due of the electric field , towards the positive end the conductor and next collision with the ions/atoms of the electrons The average speed of the free electrons with which they drift toward the positive and of the conductor under the effect of applied electric field is called drift of the electrons The motion of electrons in between two successive collisions with the atoms/ions followsA. a straight pathB. circular pathC. elliptical pathD. carved path
Answer» Correct Answer - d The free electrons moving toward the position end of the condoctor have two types of velocities (i) thermal velocity (ii) velocity due to the acceleration by virtue of force on it due to electric field. As result of it , the electron follow a curved path in between two collision in a conditor

Discussion

1483.	A cylindrical copper conductor AB length `L` areaa of cross-section a has large number of free electrons which at mean temperature move at random within the body of the conductor like the molecules of a gas. The average thermal motion at room temperature is of the enter of `10^(5)ms^(-1)` where a potential difference `V` is applied free electronic in the condictior experience , the free electrons in the conductor experience force and are accelerated towards the positive emf of the condutor on their gained kinetic energy After each collision the free electronic are angle acceleration due of the electric field , towards the positive end the conductor and next collision with the ions/atoms of the electrons The average speed of the free electrons with which they drift toward the positive and of the conductor under the effect of applied electric field is called drift of the electrons When the potential difference is applied the two ends of the conductors , an electric field existsA. outside the conductorB. inside the conductorC. both outside and inside the conductorD. no where
Answer» Correct Answer - b When a potential difference is applied across the two ends of the conductor, the electric field exits inside the conductor.

Discussion

1484.	Equivalent resistance between the points `A` and `B` (in `Omega`) .A. `(1)/(5)`B. `1(1)/(4)`C. `2(1)/(3)`D. `3(1)/(2)`
Answer» Correct Answer - C

Discussion

1485.	The value of resistance of an unknown resistor is calculated using the formula `R = V//I ` where V and I are the readings of the voltmeter and the ammeter, respectivley. Consider the circuits below. The internal resistances of the voltmeter and the ammeter `(R_V and R_G, respectively)` are finite and nonzero. , Let `R_(A) and R_(B)` be the calculated values in the two cases A and B , respectively. The relation between `R_A` and the actual value of R isA. `RgtR_(B)`B. `RgtR_(B)`C. `R=R_(B)`D. dependent upon E and r.
Answer» Correct Answer - A `R_(B)=R+R_(G)gtR`

Discussion

1486.	The value of resistance of an unknown resistor is calculated using the formula `R = V//I ` where V and I are the readings of the voltmeter and the ammeter, respectivley. Consider the circuits below. The internal resistances of the voltmeter and the ammeter `(R_V and R_G, respectively)` are finite and nonzero. , Let `R_(A) and R_(B)` be the calculated values in the two cases A and B , respectively. The relation between `R_A` and the actual value of R isA. `RgtR_(A)`B. `RltR_(A)`C. `R=R_(A)`D. dependent upon E and r.
Answer» Correct Answer - A `R_(A)=(R.R_(V))/(R+R_(V))ltR`

Discussion

1487.	Equivalent resistance between the points `A` and `B` (in `Omega`) .A. `(1)/(5)`B. `(5)/(4)`C. `(7)/(3)`D. `(7)/(2)`
Answer» Correct Answer - C

Discussion

1488.	Two wires of the same material and equal length are joined in parallel combination. If one of them has half the thickness of the other and the thinner wire has a resistance of 8 ohms , the resistance of the combination is equal toA. `(5)/(8)` ohmsB. `(8)/(5)` ohmsC. `(3)/(8)` ohmsD. `(8)/(3)` ohms
Answer» Correct Answer - B

Discussion

1489.	In the circuit shown here, what is the value of the unknown resistor R so that the total resistance of the circuit between points P and Q is also equal to R A. `3Omega`B. `sqrt(39)Omega`C. `sqrt(69)Omega`D. `10 Omega`
Answer» Correct Answer - C

Discussion

1490.	The value of resistance of an unknown resistor is calculated using the formula `R = V//I ` where V and I are the readings of the voltmeter and the ammeter, respectivley. Consider the circuits below. The internal resistances of the voltmeter and the ammeter `(R_V and R_G, respectively)` are finite and nonzero. , Let `R_(A) and R_(B)` be the calculated values in the two cases A and B , respectively. If the resistance of voltmeter is `R_(V) = 1k Omega` and the percentage error in the measurement of R (the value of R is nearly `10 Omega`)isA. zero in both casesB. non zero but equal in both casesC. more in circuit AD. more in circuit B
Answer» Correct Answer - D `%` error in case A `(R_(A)-R)/(R)xx100=((R_(V))/(R+R_(V))-1)xx100` `=(-R)/(R+R_(V))xx100approx-1%` `%` error in case B `(R_(B)-R)/(R)xx100=(R_(G))/(R)xx100approx100approx10%`

Discussion

1491.	In the circuit shown here, what is the value of the unknown resistor R so that the total resistance of the circuit between points P and Q is also equal to R A. 3 ohmsB. `sqrt(39)` ohmsC. `sqrt(69)` ohmsD. 10 ohms
Answer» Correct Answer - C

Discussion

1492.	A uniform wire of resistance `9 Omega` is cut into 3 equal parts. They are connected in form of equilateral triangle `ABC`. A cell of e.m.f. `2V` and negligible internal resistance is connected across `B` and `C`. Potential difference across `AB` isA. 1VB. 2VC. 3VD. 0.5V
Answer» Correct Answer - A

Discussion

1493.	A cylindrical copper conductor AB length `L` areaa of cross-section a has large number of free electrons which at mean temperature move at random within the body of the conductor like the molecules of a gas. The average thermal motion at room temperature is of the enter of `10^(5)ms^(-1)` where a potential difference `V` is applied free electronic in the condictior experience , the free electrons in the conductor experience force and are accelerated towards the positive emf of the condutor on their gained kinetic energy After each collision the free electronic are angle acceleration due of the electric field , towards the positive end the conductor and next collision with the ions/atoms of the electrons The average speed of the free electrons with which they drift toward the positive and of the conductor under the effect of applied electric field is called drift of the electrons The speed of electrons in a conductor is small `(= 10^(-4) ms^(-1))` when the switch is closed, the bulb at a distance glows immediately. It is so becauseA. drift velocity of electrons increase when swich in closedB. electrons are accelerated towards the position end of the conductor and their velocity increase toward the other end of the conductorC. the drifting of electrons takes place at the enter length of the connecting wire This electrics effective propagates with the speed of lightD. the electrons towards the position end and protons of condictor move toward negative end of the conductor
Answer» Correct Answer - c Knowledge based question

Discussion

1494.	A silver wire of radius `0.1 cm` carries a current of 2A. If the charge density in silver is `5.86xx10^(28)m^(-3)`, then the drif velocity isA. `0.2xx10^(-3)ms^(-1)`B. `0.4xx10^(-4)ms^(-1)`C. `0.68xx10^(-4)ms^(-1)`D. `7xx10^(-4)ms^(-1)`
Answer» Correct Answer - C

Discussion

1495.	The diameter of a copper wire is 2mm, if a steady current of 6.25 A is caused by `8.5xx10^(28) //m^(3)` electrons flowing throught it. Calculate the drift velocity of condu ction electrons.
Answer» Correct Answer - ` 0.15mm//"sec"`.

Discussion

1496.	A uniform wire of resistance `9 Omega` is cut into 3 equal parts. They are connected in form of equilateral triangle `ABC`. A cell of e.m.f. `2V` and negligible internal resistance is connected across `B` and `C`. Potential difference across `AB` isA. 0.4 V`B. 0.4 V`C. `1.2 V`D. `2.4V`
Answer» Correct Answer - a The minimum potential difference across as zero of network `= Ir//6 = 2.4 xx 1//6 = 0.4 V`

Discussion

1497.	A silver wire 1mm diameter carries a charge of 90 coulombs in 1 hours and 15 minutes. Silver contains `5.8xx10^(28)` free electrons per `cm^(3)` find the current in wire and drift velocity of the electron.
Answer» Correct Answer - `0.02A 2.74xx10^(-12)m//"sec"`

Discussion

1498.	The length of a potentiometer wire is `l`. A cell of emf `E` is balanced at a length l/3 from the positive end of the wire. If the length of the wire is increased by l/2. At what distance will the same cell give a balance point.
Answer» Correct Answer - 5 Let `E_(0)` be the pot diff applied across the total length `l(= 10cm)` of potentiometer wire Potential gradient in the first case `= (E_(0))/(l)` As per question, `E = (l)/(3)((E_(0))/(l)) = (E_(0))/(3)`….(i) potential gradient in the second case `= (E_(0))/(3l//2) = (2E_(0))/(3l)` If `x` is the desired length of potentiometer to balance the emf `E` of the cell, then `E = x xx (2E_(0))/(3l)`......(iii) From (i) and (ii) we have `(E_(0))/(3) = x xx (2E_(0))/(3l)` or `x = (l)/(2)= (10)/(2) = 5 cm`

Discussion

1499.	Electrical resistance of certain materials, known as superconductors, changes abruptly from a nonzero value of zero as their temperature is lowered below a critical temperature `T_(C) (0)`. An interesting property of super conductors is that their critical temperature becomes smaller than `T_(C) (0)` if they are placed in a magnetic field, i.e., the critical temperature `T_(C) (B)` is a function of the magnetic field strength B. The dependence of `T_(C) (B)` on B is shown in the figure. . A superconductor has `T_(C) (0) = 100 K`. When a magnetic field of 7.5 Tesla is applied , its `T_(C)` decreases to 75 K. For this material one can difinitely say that whenA. `B = 5 Tesla, T_(C) (B) = 80K`B. `B= 5Tesla, 75 K lt T_(C)(B) lt 100K`C. `B= 10 Tesla, 75ltT_(C)(B) lt100 K `D. `B = 10 Tesla, T_(C) (B) = 70K`.
Answer» Correct Answer - B (b) We know that as B increases, `T_(C)` decreases but the exact dependence is not known. Given at `B = 0, T_(C) = 100K` and at `B= 7.5 T, T_(C) = 75K` `:. At B = 5T, T_(C) should be between 75 K and 100K. `

Discussion

1500.	Electrical resistance of certain materials, known as superconductors, changes abruptly from a nonzero value of zero as their temperature is lowered below a critical temperature `T_(C) (0)`. An interesting property of super conductors is that their critical temperature becomes smaller than `T_(C) (0)` if they are placed in a magnetic field, i.e., the critical temperature `T_(C) (B)` is a function of the magnetic field strength B. The dependence of `T_(C) (B)` on B is shown in the figure. . In the graphs below, the resistance R of a superconductor is shown as a function of its temperature T for two different magnetic fields `B_1`(solid line) and `B_2` (dashed line). If `B_2` is larget than `B_1` which of the following graphs shows the correct variation of R with T in these fields?A. B. C. D.
Answer» Correct Answer - A (a) From the given graph it is clear that with increase of the magnitude of magnetic field (B), the critical temperature `T_(C) (B)` decreases. Given `B_2gtB_1`. Therefore for `B_2`, the temperature at which the resistance becomes zero should be less. The above statement is true for graph (a).

Discussion

Explore topic-wise InterviewSolutions in .

The direction of current density is ……. To the direction of friff velocity of electrons in the conductor

A Steady current flows in a metalic conductor of non uniform cross section. The quantity/quantities which remain constant along the length of the conductor is/areA. Current,electric field and drift speedB. drift speed onlyC. current and drift speedD. current only

In a closed loop when current has not been reached the stedy start , the current through different cross-section of the irregular shaped conductor of a particular instant would have……… values.

A charged capacitor `(C_(1) = 3 mu F)` is getting discharged in the circuit shown. When the current `I` was observed to be 2.5 A, switch ‘S’ was opened. Determine the amount of heat that will be liberated in the circuit after ‘S’ is opened.

In the circuit elements given below, all individual resistors are identical. The resistance between P and Q in the different cases is A. a) `3R`B. b) `5R//6`C. c) `R//2`D. d) R

Which of the following quantities do not change when a resistor connected to a battery is heated due to the current?A. drift speedB. resistivityC. resistanceD. number of free electrons

A current passes through a wire of nonuniform cross-section. Which of the following quantites are independent of the cross section?A. the charge crossing in a given time internalB. drift speedC. current densityD. free-electron density.

A current passes through a wire of nonuniform cross-section. Which of the following quantites are independent of the cross section?A. free electron densityB. current densityC. drift speedD. the charge crossing in a given time internal

A current passes through a wire of nonuniform cross-section. Which of the following quantites are independent of the cross section?A. the charge crossing in a given time inverval.B. drift speedC. current densityD. free-electron density

Drift velocity `v_(d)` varies with the intensity of electric field as per their relationA. `v_(d)alphaE`B. `v_(d)alphaE^(2)`C. `v_(d)alphasqrt(E)`D. `v_(d)=` constant

Drift velocity `v_(d)` varies with the intensity of electric field as per their relationA. `v_(d)propE`B. `v_(d)prop(1)/(E)`C. `v_(d)="constant"`D. `v_(d)propE^(2)`

An electric wire of length ‘ I ’ and area of cross-section a has a resistance R ohm s. Another wire of the same material having same length and area of cross-section 4a has a resistance ofA. `4R`B. `R//4`C. `R//16`D. `16R`

If n, e, `tau`, m, are representing electron density charge, relaxation time and mass of an electron respectively then the resistance of wire of length 1 and cross sectional area A is given byA. `(ml)/("ne"^(2)tauA)`B. `(mtauA)/("ne"^(2)l)`C. `("ne"^(2)tauA)/(ml)`D. `("ne"^(2)A)/(ml)`

For which of the following the resistance decreases on increasing the temperatureA. CopperB. TungstenC. GermaniumD. Aluminium

If n, e, `tau`, m, are representing electron density charge, relaxation time and mass of an electron respectively then the resistance of wire of length 1 and cross sectional area A is given byA. `(ml)/(n e^(2)tauA)`B. `(m tau^(2)A)/(n e^(2)l)`C. `(n e^(2) tauA)/(2ml)`D. `(n e^(2)A)/(2mtaul)`

The relaxation time in conductorsA. Increases with the increase of temperatureB. Decreases with the increase of temperatureC. It does not depend on temperatureD. All of sudden changes at 400 K

The relaxation time in conductorsA. Increase with the increase of temperatureB. Decrease with the increase of temperatureC. It does not depent on temperatureD. All of sudden changes at `400 K`

Drift velocity `v_(d)` varies with the intensity of electric field as per the relationA. `v_(d) prop E`B. `v_(d) prop (1)/(E)`C. `v_(d) =` constantD. `v_(d) prop E^(2)`

Find the potential difference across each of the four batteries `B_1, B_2, B_3` and `B_4` as shown in the figure.

1 ampere current is equivalent toA. `6.25xx10^(-18)"electrons s"^(-1)`B. `2.25xx10^(-18)A"electrons s"^(-1)`C. `6.25xx10^(14)"electrons s"^(-1)`D. `2.25xx10^(14)"electrons s"^(-1)`

A current in a wire is given by the equation, . `I=2t^(2)-3t+1`, the charge through cross section of : wire in time interval t=3s to t=5s isA. 32.33CB. 43.34CC. 45.5CD. 42C

It was found that resistance of a cylindrical specimen of a wire does not change with small change in temperature. If its temperature coefficient of resistivity is `alpha_(R)` then find its thermal expansion coefficient `(alpha)`.

A bulb B is connected to a source having constant emf and some internal resistance. A variable resistance R is connected in parallel to the bulb. If the resistance R is increased, how will it affect the- (a) Brightness of the bulb? (b) Power spent by the source ?

The length of a potentiometer wire is `l`. A cell of emf `E` is balanced at a length l/3 from the positive end of the wire. If the length of the wire is increased by l/2. At what distance will the same cell give a balance point.A. `(2l)/(3)`B. `(l)/(2)`C. `(l)/(6)`D. `(4l)/(3)`

An electron revolves in a circule at the rate of `10^(19)` rounds per second. The rquivlent current is `(e=1.6xx10^(-19)C)`A. `1.0 A`B. `1.6A`C. `2.0A`D. `2.6A`

Equivalent resistance between the points `A` and `B` (in `Omega`) .A. `(1)/(5)`B. `1(1)/(4)`C. `2(1)/(3)`D. `3(1)/(2)`

Equivalent resistance between the points `A` and `B` (in `Omega`) .A. `(1)/(5)`B. `(5)/(4)`C. `(7)/(3)`D. `(7)/(2)`

Two wires of the same material and equal length are joined in parallel combination. If one of them has half the thickness of the other and the thinner wire has a resistance of 8 ohms , the resistance of the combination is equal toA. `(5)/(8)` ohmsB. `(8)/(5)` ohmsC. `(3)/(8)` ohmsD. `(8)/(3)` ohms

In the circuit shown here, what is the value of the unknown resistor R so that the total resistance of the circuit between points P and Q is also equal to R A. `3Omega`B. `sqrt(39)Omega`C. `sqrt(69)Omega`D. `10 Omega`

In the circuit shown here, what is the value of the unknown resistor R so that the total resistance of the circuit between points P and Q is also equal to R A. 3 ohmsB. `sqrt(39)` ohmsC. `sqrt(69)` ohmsD. 10 ohms

A uniform wire of resistance `9 Omega` is cut into 3 equal parts. They are connected in form of equilateral triangle `ABC`. A cell of e.m.f. `2V` and negligible internal resistance is connected across `B` and `C`. Potential difference across `AB` isA. 1VB. 2VC. 3VD. 0.5V

A silver wire of radius `0.1 cm` carries a current of 2A. If the charge density in silver is `5.86xx10^(28)m^(-3)`, then the drif velocity isA. `0.2xx10^(-3)ms^(-1)`B. `0.4xx10^(-4)ms^(-1)`C. `0.68xx10^(-4)ms^(-1)`D. `7xx10^(-4)ms^(-1)`

The diameter of a copper wire is 2mm, if a steady current of 6.25 A is caused by `8.5xx10^(28) //m^(3)` electrons flowing throught it. Calculate the drift velocity of condu ction electrons.

A uniform wire of resistance `9 Omega` is cut into 3 equal parts. They are connected in form of equilateral triangle `ABC`. A cell of e.m.f. `2V` and negligible internal resistance is connected across `B` and `C`. Potential difference across `AB` isA. 0.4 V`B. 0.4 V`C. `1.2 V`D. `2.4V`

A silver wire 1mm diameter carries a charge of 90 coulombs in 1 hours and 15 minutes. Silver contains `5.8xx10^(28)` free electrons per `cm^(3)` find the current in wire and drift velocity of the electron.

The length of a potentiometer wire is `l`. A cell of emf `E` is balanced at a length l/3 from the positive end of the wire. If the length of the wire is increased by l/2. At what distance will the same cell give a balance point.