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Chapter 3 Current Electricity Solutions

Question - 1 : -

The storage batteryof a car has an emf of 12 V. If the internal resistance of the battery is 0.4Ω, what is the maximum current that can be drawn from the battery?

Answer - 1 : - The maximum current will be obtained when no external resistance isoffered by wire joining the two terminals.

Question - 2 : -

A battery of emf 10V and internal resistance 3 Ω is connected to a resistor. If the current in thecircuit is 0.5 A, what is the resistance of the resistor? What is the terminalvoltage of the battery when the circuit is closed?

Answer - 2 : -

Question - 3 : -

(a) Threeresistors 1 Ω, 2 Ω, and 3 Ω are combined in series. What is the totalresistance of the combination?
(b) If the combination is connected to a battery of emf 12 V andnegligible internal resistance, obtain the potential drop across each resistor.

Answer - 3 : - (a) Total resistance of the combination in series

Question - 4 : -

(a) Threeresistors 2Ω, 4Ω and 5Ω are combined in parallel. What is the total resistanceof the combination?
(b) If the combination is connected to a battery of emf 20 V andnegligible internal resistance. Determine the current through each resistor,and the total current drawn from the battery.

Answer - 4 : - (a) Total resistance of the combination in parallel

(b) Potential of 20 V will be same across each resistor, so current

Question - 5 : -

At room temperature (27.0°C) theresistance of a heating element is 100 O. What is the temperature of theelement if the resistance is found to be 117 Ω, given that the temperaturecoefficient of the material of the resistor is 1.70 × 103 0C-1.

Answer - 5 : -

Question - 6 : - A negligibly small current is passed through awire of length 15 m and uniform cross-section 6.0 × 10-7 m2,and its resistance is measured to be 5.0 Ω. What is the resistivity of thematerial at the temperature of the experiment?

Answer - 6 : -

Question - 7 : - A silver wire has a resistance of 2.1 Ω, at27.5°C and a resistance of 2.7 Ω at 100°C. Determine the temperaturecoefficient of resistivity of silver.

Answer - 7 : -

Question - 8 : - A heating element using nichrome connected toa 230 V supply draws an initial current of 3.2 A which settles after a fewseconds to a steady value of 2.8 A. What is the steady temperature of theheating element if the room temperature is 27.0 °C ?Temperature coefficient ofresistance of nichrome averaged over the temperature range involved is 1.70 ×10-4 °C-1.

Answer - 8 : - At room temperature 27 °C, the resistance of the heating element.

Question - 9 : - Determine the current in each branch of thenetwork shown in figure.

Answer - 9 : - Marti Let us first distribute the current in different branches. Now, eΩactions for different loops using Kirchhoff’s IInd law,

Question - 10 : - (a) In a meter bridge as shown in figure,the balance point is found to be at 39.5 cm from the end A, when the resistoris of 12.5 Ω. Determine the resistance of x. Why are the connection betweenresistors in a Wheatstone or meter bridge made of thick copper strips?
(b) Determine the balance point of thebridge above if x and are interchanged.
(c) What happens if the galvanometer and cell are interchanged at thebalance point of the bridge? Would the galvanometer show any current?

Answer - 10 : - (a)

The connections are made of thick copper strips so as to providenegligible resistance by connecting wires.
(b) If x and Y areinterchanged the balance point will be at 60.5 cm from A.
(c) In balanced conditionof the bridge, the cell and the galvanometer can be exchanged, the galvanometerwill still show zero deflection.

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