InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Name a substance whose resistance almost remains unchanged by increase of temperature. |
| Answer» Manganin (an alloy of Cu, Ni and mn). | |
| 2. |
Two resistors with resistances `10 Omega and 15 Omega` are to be connected to a battery of `emf 12 V` so as to obtain : (i) minimum current (ii) maximum current. How will you connect the resistances in each case ? Calculate the strength of the total current in the circuit in the two cases. |
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Answer» Correct Answer - `2 A` To obtain minimum current, the two resistors should be connected in series so that the equivalent resistance, `R_s = 10 Omega + 15 Omega = 25 Omega`. Thus, `I_(min) = (12 V)/(25 Omega) = 0.48 A`. To obtain maximum current, the two resistors should be connected in parallel so that the equivalent resistance, `R_p = (15 Omega xx 10 Omega)/(15 Omega + 10 Omega) = 6 Omega`. Thus, `I_(max) = (12 V)/(6 Omega) = 2 A`. |
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| 3. |
An electric geyser has the rating `2000 W-220 V` marked on it. What should be the minimum current rating (in whole number) of the fuse-wire to be used ? |
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Answer» Correct Answer - `10 A` `I = P//V = 2000 W//220 V = 9.1 A`. Thus, the minimum current rating (in whole number) of the fuse wire is `10 A`. |
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| 4. |
Assertion and Reason type questionAssertion: One kilowatt hour is known as one unit of electrical energy. Reason: 1 kWh = 3.6 × 106 J (a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion. (b) If both the assertion and the reason are true, but the reason is not the correct explanation of the assertion. (c) If the assertion is true, but the reason is false. (d) If the assertion is false, but the reason is true. |
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Answer» (a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion. |
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| 5. |
Choose the correct statement: When the same current(i) flows through tow circuits as shown in the figures, then (assume that all bulbs are identical) (A) bulbs in first combination glow with more brightness. (B) bulbs in second combination glow with more brightness. (C) bulbs in both the combination glow with equal brightness. A. Only (A) is trueB. Only (B) is trueC. Only (C) is trueD. Cannot be determined. |
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Answer» Correct Answer - A When same current flows through the circuit the bulbs in series combination glow with more brightness than the bulbs in parallel combination. |
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| 6. |
400 J of heat is produced in 4 s in a 4 Ω resistor. Find potential difference across the resistor. |
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Answer» V2/R x t=400 V2=400 V=20 Volt |
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| 7. |
`100 J` of heat are produced each second in a `4 Omega` resistance. Find the potential difference across the resistor. |
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Answer» `H=100J, R=4 Omega, t=1 s, V=?` From Eq. (12.21) we have the current through the resistor as `I= sqrt(H//Rt)` `=sqrt[100J//(4Omegaxx1s)]` =5A Thus the potential difference across the resistor, V [ from Eq. [(12.5)] is V=iR `=5 Axx4 Omega` = 20 V. |
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| 8. |
When a current of 4.0 A passes through a certain resistor for 10 minutes, 2.88 x 104 J of heat are produced. Calculate :(a) the power of the resistor.(b) the voltage across the resistor |
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Answer» Given I = 4 amp, t = 10min = 10 x 60 = 600sec, H = 2.88 x 104J (a) We have H = I2RT 28800 = 42 x R X 600 R = 3 ohms We know that P = I2 x R = 42 x 3 P = 48 W (b) V = ? we know that V = IR V = 4 x 3 V = 12V |
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| 9. |
Explain applications of heating effect. |
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Answer» Electric Heating Device: The heating effect of electric current is used in many home appliances such as electric iron, electric toaster, electric oven, electric heater, geyser, etc. In these appliances Nichrome, which is an alloy of Nickel and Chromium is used as the heating element. Because: (i) it has high resistivity, (ii) it has a highmelting point, (iii) it is not easily oxidized. Fuse Wire : The fuse wire is connected in series, in an electric circuit. When a large current passes through the circuit, the fuse wire melts due to Joule’s heating effect and hence the circuit gets disconnected. Therefore, the circuit and the electric appliances are saved from any damage. The fuse wire is made up of a material whose melting point is relatively low. Filament in bulbs : In electric bulbs, a small wire is used, known as filament. The filament is made up of a material whose melting point is very high. When current passes through this wire, heat is produced in the filament. When the filament is heated, it glows and gives out light. Tungsten is the commonly used material to make the filament in bulbs. |
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| 10. |
Write Joule’s Law of Heating. |
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Answer» When a current I flows through a resistor R heat is produced. H = I2Rt, this is Joule’s law of heating. |
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| 11. |
State and explain Joule’s law of heating. |
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Answer» Joule's law of heating states that heat produced in joules when a current of I amperes given by H = I2Rt. Thus the heat produced in a write is directly proportional to : (i) Square of current (ii) Resistance of wire (iii) Time for which current is passed |
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| 12. |
What is Joule’s heating effect? How can it be demonstrated experimentally? List its four applications in daily life |
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Answer» According to Joules heating effect heat produces in a resistor is a) Directly proportional to square of current for the given resistor. b) Directly proportional to resistance for a given current, c) Directly proportional to the time of current flowing through the resistor. This can be expressed as H = I2Rt H is heating effect, I is electric current, R is resistance and t is time Experiment to demonstrate Joules law of heating
Observation:
Application: Electric toaster, oven, electric kettle and electric heater etc. work on the basis of leafing effect of current. |
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| 13. |
(a) State Joule’s law of heating(b) An alloy of nickel and chromium is used as the heating element. Why? (c) How does a fuse wire protect electrical appliances? |
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Answer» (a) Joule’s law of heating states that the heat produced in any resistor is: 1. directly proportional to the square of the current passing through the resistor. 2. directly proportional to the resistance of the resistor. 3. directly proportional to the time for which the current is passing through the resistor. (b) Because, 1. It has high resistivity, 2. It has a high melting point, 3. It is not easily oxidized. (c) When a large current passes through the circuit, the fuse wire melts due to Joule’s heating effect and hence the circuit gets disconnected. Therefore, the circuit and the electric appliances are saved from any damage. |
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| 14. |
A refrigerator having a power rating of 350W operates for 10 hours a day. Calculate the cost of electrical energy to operate if for a month of 30 days. The rate of electrical energy is Rs. 340 per kWh. |
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Answer» Electrical energy, `E = P xx t` Power, `P = 350 W` `= (350)/(1000) kW` `= 0.35 kW` And, Time, `t = 10 xx 30` hours `= 300 h` Now, putting these values of P and t in the formula, `E = P xx t` We get: `E = 0.35 xx 300 kWh` `= 105 kWh` Thus, the electrical energy consumed by the refrigerator in a month of 30 days is 105 kilowatt-hours. Now, Cost of 1 kWh of electricity = Rs. 3.40 So, Cost of 105 kWh of electricity = Rs. `3.40 xx 105` = Rs. 357` |
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| 15. |
Why does the cord of an electric heater not glow while the heating element does? |
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Answer» In cord of an electric heater, as current flows these become hot arid glows but in case of electric heater this will not happen. |
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| 16. |
State Joules low of heating and give its expression. |
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Answer» According to Joule’s law of heating the heat produced in the resistor is 1. Directly proportional to the square of the current through the resistor 2. Directly proportional to the resistance of the given resistor 3. Directly proportional to the time for which the current flows. Mathematically, Joule’s law of heating is given by H = i2Rt |
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| 17. |
An electric heater rated 800 W operates 6 h/day. Find the cost of energy to operate it for 30 days at Rs.3.00 per unit. |
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Answer» Energy consumed=P x t =800 x 6 x 30 =144000 Wh =144 kWh Cost of electricity = 144 x 3 = Rs. 432. |
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| 18. |
Why the cord of a heating element does not glow while the heating element glows? |
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Answer» The glow of an element is due to the power dissipation of the element. The power of an element is given by P = i2R As the resistance of the heating element is higher than the cords, the power dissipation of the heating element is greater and it glows. |
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| 19. |
Fill in the blanks. 1. _____ are the materials which allow electric current to pass through them. 2. Flow of electricity through a closed circuit is _____ 3. _____ is the device used to close or open an electric circuit. 4. The long perpendicular line in the electrical symbol represents its _____ terminal. 5. The combination of two or more cells is called a _____ |
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Answer» 1. conductors 2. a complete electric circuit 3. Key or Switch 4. positive 5. Battery |
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| 20. |
How does a bulb with filament glow? |
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Answer» 1. When electric current is passed through the filament (made with Tungsten), it becomes red hot and further becomes bright white. 2. This bright white glow of the filament gives light. |
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| 21. |
(a) How much current will an electric bulb draw from a `220 V` source, if the resistance of the bulb filament is `1200 Omega` ? (b) How much current will an electric heater draw from a `220 V` source, if the resistance of the heater coil is `100 Omega` ? |
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Answer» (a)`" We are given V" = 220 V, R=1200 Omega` From Eq. (12.6), we have the current I `= 220V//1200 Omega=0.18 A`. (b) we are given, `V=220 V, R=100 Omega`. Form Eq. (12.6), we have the current `I= 220 V // 100 Omega = 2.2 A`. Note the difference of current drawn by an electric bulb and electric heater form the same 220 V source ! |
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| 22. |
Which meterial is used to make filament of bulb? |
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Answer» The filament of an electric bulb, is made of Tungesten. |
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| 23. |
Which of the following is the most likely temperature of the filament of an electric ligth bulb when it is working on the normal 220 V supply line?A. `500^(@)C`B. `1500^(@)C`C. `2500^(@)C`D. `4500^(@)C` |
| Answer» Correct Answer - C | |
| 24. |
In a filament type light bulb, most of the electric power consumed appears as:A. visible lightB. infra-red-raysC. ultraviolet raysD. fluorescent light |
| Answer» Correct Answer - B | |
| 25. |
True or False. If False, give the correct statement.1. In a parallel circuit, the electricity has more than one path.2. To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell.3. The switch is used to close or open an electric circuit.4. Pure water is a good conductor of electricity.5. Secondary cell can be used only once. |
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Answer» 1. True 2. False. To make a battery of two cells, the negative terminal of one cell is connected to the positive terminal of the other cell. (OR) To make a battery of two cells, the positive terminal of one cell is connected to the negative terminal of the other cells. 3. True 4. False. Impure water is a good conductor of electricity. 5. False. Primary cells can be used only once. |
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| 26. |
Why the filament of bulb has high melting point ? |
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Answer» A filament is made up of a substance having a high melting point because a bulb lights up heating the filament. The heated filament is the source of light and if the melting point of filament's substance is low, it may melt. |
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| 27. |
How many cells are required to make a battery? |
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Answer» 1. Two or more cells are combined to make a battery. 2. A battery is a collection of cells. |
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| 28. |
Where are Windmills located in Tamil Nadu? |
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Answer» 1. Aralvaimozhi in Kanyakumari District. 2. Kayatharu in Tirunelveli District. |
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| 29. |
What determines the rate at which energy is delivered by a current ? |
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Answer» Electric power determines the rate at which energy is delivered by a current. |
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| 30. |
Match the following :1.thermal power station(a)Kinetic energy2.Hydel power station(b)Nuclear energy is converted into mechanical energy and then electrical energy3.Atomic power stations(c)Wind energy is used to produce electricity.4.Wingmills(d)Heat energy is converted into electrical energy. |
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Answer» 1. – d 2. – a 3. – b 4. – c |
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| 31. |
Analogy.1. Thermal power station : Neyveli. Hydel power station : ________2. Kayatharu in Tirunelveli district: Wind mills. Koodankulam in Tirunelveli district: ________3. Primary cells : Toys Secondary cells: ________4. Bulbs are connected in series : Series circuit. Bulbs are connected in parallel: ________ |
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Answer» 1. Mettur 2. Atomic power station. 3. Emergency lamps. 4. Parallel circuit. |
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| 32. |
Where are the Hydel power stations located in Tamil Nadu? |
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Answer» 1. Mettur in Salem District. 2. Papanasam in Tirunelveli District. |
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| 33. |
Name the physical quantity that determines the rate at which energy is delivered by an electric current. State and define the unit of this physical quantity. |
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Answer» Quantity - Electric power Unit: Watt 1 Watt is the power consumed by a device that carries 1 A of current when operated at a: potential difference oi 1 V. |
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| 34. |
What is heating effect of the electric current? |
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Answer» 1. The wire or component gets hot when an electric current passes through them, 2. This is known as heating effect of the electric current. |
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| 35. |
Fill in the blanks. 1. Hydel electricity is produced in _____ in Tirunelveli district. 2. In Thermal power station _____ is used as fuel. 3. _____ Cells used in automobiles like cars and buses are large and very heavy.4. The rate of flow of electric charges in a circuit is called ______ 5. ______ is a kind of fish which is able to produce electric current. 6. ______ are used to connect devices. 7. _____ was an American inventor, who invented electric bulb. |
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Answer» 1. PaPanasam 2. Coal or diesel 3. Secondary 4. Electric Current 5. Electric Eel 6. Connecting Wires 7. Thomas Alva Edison |
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| 36. |
In the circuit diagram below, 10 units of electric charge move past point x every second What is the current in the circuit ________.(a) 10 A (b) 1 A (c) 10 V (d) 1 V |
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Answer» Correct answer is (a) 10 A |
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| 37. |
Define electric cell. What is the direction of electric current in a cell? |
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Answer» 1. The simplest sources of an electric current is an electric cell and it has a positive terminal and a negative terminal. 2. In electric cell the current starts from positive terminal of the cell, passes through the equipment connected to it, and terminates at the negative terminal of the cell. |
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| 38. |
What determines the rate at which energy is delivered by a current? |
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Answer» Electric power. |
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| 39. |
Write the analogy between water current and electric current. |
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Answer» 1. Water molecules flow towards a point of lower elevation. 2. Electric charges flow towards a point of lower voltage. |
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| 40. |
Thomas Alva Edison invented more than ________ useful inventions which are used in homes. (a) 100 (b) 10 (c) 500 (d) 1000 |
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Answer» Correct answer is (d) 1000 |
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| 41. |
________ is an instrument used in electric circuits to find the quantity of current flowing through the circuit. (a) Volt meter (b) Ammeter (c) Cell (d) Key |
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Answer» (b) Aniniele |
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| 42. |
What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series? |
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Answer» (i) In a parallel circuit, if one electrical appliance stops working due to some defect, then all other appliances keep working normally. In a series circuit, if one electrical appliance stops working due to some defect, then all other appliances also stop working. |
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| 43. |
Which circuits are used in homes? (a) Parallel circuit (b) Serial circuit (c) Simple circuit (d) None |
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Answer» (a) Parallel circuit |
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| 44. |
What happens when an electric current passes through wires used for making electric circuits and through the elements of some electric appliances? |
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Answer» 1. The wires used for making electric circuits do not normally become hot. 2. On the other hand, the elements of some electric appliances become so hot that they are easily visible. 3. The filament of an electric bulb gets heated to such a high temperature that is starts glowing and giving out light. |
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| 45. |
Differentiate parallel and serial circuits. |
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Answer» Parallel circuits: 1. It is connected by branches 2. Voltage remains the same across each component of the circuit 3. Each bulb is fully powered. 4. All bulbs stay lit if one goes out. Serial circuits: 1. It consist of single loop connection. 2. Current remains same in all parts of the circuit. 3. All the bulbs share power. 4. All bulbs go out if one goes out. |
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| 46. |
Match the following :1. Cell – used to open or close a circuit 2. Switch – safety device used in electric circuit 3. Circuit – A complete path for the flow of an electric current 4. Miniature circuit Breaker- Reset by hand, circuit becomes complete once again 5. Fuse – A device which converts chemical energy into electrical energy |
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Answer» 1. Cell – A device which converts chemical energy into electrical energy 2. Switch – used to open or close a circuit 3. Circuit – A complete path for the flow of an electric current 4. Miniature circuit Breaker – Reset by hand, circuit becomes complete once again 5. Fuse – safety device used in electric circuit |
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| 47. |
Why parallel circuits are used in homes? |
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Answer» Parallel circuits are used in homes, because if any one of the bulb is damaged or disconnected, the other part of the circuit will work. |
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| 48. |
Match the following :1.Bulb(a)2.Cell(b)3.Battery(c)4.Switch (Closed)(d) |
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Answer» 1. (b) 2. (c) 3. (d) 4. (a) |
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| 49. |
What are the advantages of connecting electrical devices in parallel with the battery instead of connected them in series ? |
| Answer» There is no division of voltage among the appliances when connected in parallel. The potential difference across each appliance is equal to the supplied voltage. The total effective resistance of the crcuit can be reduced by connecting electrical appliances in parallel. | |
| 50. |
Why should the resistance of : (a) an ammeter be very small ? (b) a voltmeter be very large ? |
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Answer» Solution : (a) The resistance of an ammeter should be very small so that it may not change the value of the current flowing in the circuit. (b) The resistance of a voltmeter should be very large so that it takes a negligible current from the current. |
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