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(Managanin).

(i) Let ε be emf and r the internal resistance of each cell. The equation of terminal potential difference

V = ε_eff – i r_int becomes

V = 3ε –i r_int …(i)

Where r_int is effective (total) internal resistance.

From fig., when i = 0, V = 6.0 V

∴ From (i), 6 = 3ε - 0 \(\Rightarrow \epsilon=\frac{6}{3}=2V\)

i.e., emf of each cell, ε = 2 V

Thus, emf of each cell, ε = 2V

Potential difference, E = 6/3 = 2 V

Internal resistance, r = \(\frac{E}{I} = \frac{6}{1}\) = 6 ohm

Given, three cells are connected in series,

r' = r/3 = 6/3 = 2 ohm

We know that for a circuit

V = E_eq - Ir_eq    ....(i)

From graph, when I = 0 A, then V = 6 V and when I = 1 A then V = 0 V

Putting V = 6 V and I = 0 A in eq (i)

6 = E_eq - 0.r_eq \(\Rightarrow\) E_eq = 6 V

E_eq = ε₁ + ε₂ + _ε3 \(\Rightarrow\) ε₁ = ε₂ = ε₃ = ε = \(\frac{E}{3}\) = 2 V

And, when I = 1 A, and V  = 0 V

0 = 6 - 1. r_eq \(\Rightarrow\) r_eq = 6 Ω

r_eq = r₁ + r₂ + r₃ \(\Rightarrow\) r₁ = r₂ = r₃ = r = \(\frac{R}{3}\) = 2 ohm

Nichrome wire gets heated up more.

Heat dissipated in a wire is given by

\(H=I^2Rt\)

\(H=I^2 \,\frac{pl}{A}t\) \((\because\,R=\frac{pl}{A})\)

Here, radius is same, hence area (A) is same. Also, current (I) and length (l) are same.

\(\therefore \,H\infty\,r\)

But P_nichorme > P_copper

∴ H_nichrome > H_copper

The answer is (C) 30 Ω

The answer is (C) 4:1

The answer is (A) R

The rate of flow of charge through any wire is called Current.

The net flow of charge at any point in the conductor is Zero.

Data : G = 38 Ω, 

\(\cfrac{I_g}I\) = \(\cfrac1{20}\)

I_g = \(\left(\cfrac{S}{S+G}\right)I\)

∴ \(\cfrac{I_g}I\) = \(\cfrac{S}{S+G}\)

∴ \(\cfrac1{20}\) = \(\cfrac{S}{S+38}\)

∴ S + 38 = 20 S 

∴ 19 S = 38 

∴ S = 2 Ω

This is the required value of the shunt.

The average time that elapses between two successive collisions of an electron with fixed atoms or ions in the conductor is called relaxation time. 

Mobility (μ) is defined as the magnitude of drift velocity (v_d) per unit electric field (E). i.e. μ = (v_d/E)

Relaxation time decreases with increase in temperature. 

Mobility is defined as the magnitude of the drift velocity per unit electric field. 

μ = V_d/E = lτ/m

where τ is the average collision time for electrons. 

The SI unit of mobility is m² /Vs or m² V^–1 s^–1

Resistivity of a material, \(p=\frac{m}{ne^2r}\)

Where m is mass, e is charge on charge carrier, n is number density and τ is relaxation time.

For a metallic conductor: When temperature of a metal increases, the number of collisions of electrons with ion-lattice increases, so relaxation time decreases, as

resistivity \(P\,\infty \frac{1}{T},\) so resistivity of material increases with rise of temperature.

For a semiconductor: When temperature increases, the covalent bonds between valence electrons of atoms of semiconductor break, so more charge carriers (electrons and holes) becomes free. In other words the number density of charge carriers

increases \(P\,\infty \frac{1}{n},\) so resistivity of semiconductor decreases with the rise of temperature.

Current density vector J is the current flowing through a conductor per unit are of cross section, it is a vector quantity and has the direction same as current.

l = vector J.A

Magnitude of current density

J = l/A = nev_d

Correct option is: (c) electrons

Correct option is: (a) zero

The unit of resistivity is ohm metre (Qm).

Earth wire is generally yellow or green colour, it is connected to a metal plate buried deep underground near the house and is for safety purpose.

Correct option is: (c) positive, negative

Those substances which have very low electrical resistance are called conductors of electricity.

From positive terminal of battery to negative terminal of battery through the external circuit. It is opposite to electron flow direction. 

(1) drift velocity : It is defined as the average velocity gained by the free electrons of a conductor in the opposite of the externally applied electric field. 

(2) relaxation time : The average time that elapses between two successive collisions of an electron with fixed atoms or ions in the conductor is called relaxation time. 

C. chemical processes

It states that the heat developed in an electrical circuit due to the flow of current varies directly as:

1. the square of the current 

2. the resistance of the circuit and 

3. the time of flow.

H = I² R?

Correct answer is (a) straight line

Every metal conductor has large number of free electrons which move randomly at room temperature. Their average thermal velocity at any instant is zero. When a potential difference is applied across the ends of a conductor, an electric field is set up. Due to it, the free electrons of the conductor experience force due to electric field and drift towards the positive end of the conductor, causing electric current. 

6 ohm 12V bulb is  calculate the resistance.

When current flows through a resistor, some of the electrical energy delivered to the resistor is converted into heat energy and it is dissipated. This heating effect of current is known as Joule’s heating effect.

V= IR, R= V/I, R= 6/3 =2 ohm

Conversion of temperature differences into electrical voltage and vice versa is known as thermoelectric effect.

(i) No

(ii) High

(iii) Resistance increased when the temperature was increased

(iv)

• Area of cross-section 
• Nature of the material 
• Length 
• Temperature

Thermopile is a device used to detect thermal radiation. It works on the principle of seebeck effect.

(1) False. The SI unit of charge is coulomb. 

(2) False. Voltmeter is ahvays connected in parallel with the device.

(3) True 

(4) True 

(5) False. Resistivity of pure metals is less than alloys. 

(6) False. Resistance in series arrangement is used to increase resistance of circuit. 

(7) True 

(8) False. Charges are measured in coulomb. 

(9) False. The unit of potential difference is volt. 

(10) False. Resistance of a conductor is directly proportional to the length of the conductor. 

(11) False. Ammeter is connected in series to the cell to measure current.

(12) False. Fuse is made of wire having low melting point.

A material with a negative temperature coefficient is called a thermistor. 

Eg:

1. Insulator 

2. Semiconductor.

(i) Insulator

(ii) Super conductor

(iii) R_s = R₁ + R₂

(iv) Ampere

(v) Volt

Correct option is (B) 30 cm

Correct option is (C) 0.1 Ω

Correct option is (A) 0.1 V/m

The applications (uses) of the potentiometer :

1. Voltage divider : The potentiometer can be used as a voltage divider to change the output voltage of a voltage supply. 

2. Audio control: Sliding potentiometers are commonly used in modern low-power audio systems as audio control devices. Both sliding (faders) and rotary potentiometers (knobs) are regularly used for frequency attenuation, loudness control and for controlling different characteristics of audio signals.

3. Potentiometer as a sensor: If the slider of the potentiometer is connected to the moving part of a machine, it can work as a motion sensor. A small displacement of the moving part causes a change in potential which is further amplified using an amplifier circuit. The potential difference is calibrated in terms of displacement of the moving part. 

4. To measure the emf (for this, the emf of the standard cell and potential gradient must be known). 

5. To compare the emf’s of two cells. 

6. To determine the internal resistance of a cell.

A voltmeter should ideally have an infinite resistance so that it does not draw any current from the circuit. However a voltmeter cannot be designed to have infinite resistance. A potentiometer does not draw any current from the circuit at the null point. Therefore, it gives more accurate measurement. Thus, it acts as an ideal voltmeter.

Potential difference between two points of a current carrying conductor is directly proportional to the length of the wire between two points.

1. Joules law of heating

2. Heat developed in the conductor H = I² R If current is doubled, Heat developed becomes 4 times.

1. True.

2. When temperature increases, the amplitude of vibration of atom increases. Hence relaxation time decreases. Hence resistivity of metal increases according to the equation

\(ρ=\frac{m}{ne^2\tau}\)

3.  A ....... Carbon

B ....... Manganin

C ............. Iron.

4.  The temperature coefficient of resistance of manganin, eureka and constantan, etc are zero. Hence they are used in making standard resistance coils.

1. Its measurement uses null method.

2. Principle:

Potential difference between two points of a current carrying conductor (having uniform thickness) is directly proportional to the length of the wire between two points.

3. I = 600 cm, I = 350 cm

\(r=R\Big(\frac{I-I_1}{I_1}\Big)\) r = 3 \(\Big(\frac{600-350}{350}\Big)\)

= \(\frac{3\times250}{350}\) = 2.1 Ω