Current Electricity Multiple Choice Questions and Answers for Practice

16. In a potentiometer of 10 wires, the balance point is obtained on the 7th wire. To shift the balance point to 9th wire, we should

1. decrease resistance in the main circuit.
2. increase resistance in the main circuit.
3. decrease resistance in series with the cell whose emf is to be measured.
4. increase resistance in series with the cell whose emf is to be determined.

17. In a Wheatstone bridge if the battery and galvanometer are interchanged then the deflection in galvanometer will

1. change in previous direction
2. not change
3. change in opposite direction
4. none of these.

18. In a Wheatstone‘s bridge all the four arms have equal resistance R. If the resistance of the galvanometer arm is also R, the equivalent resistance of the combination as seen by the battery is

1. R/2
2. R
3. 2R
4. R/4

19. In an experiment with potentiometer, null point with a cell is found at 240 cm. When the cell is shunted with a resistance 2 Ω, the null point becomes 120 cm internal resistance of cell is :

1. 4 Ω
2. 2 Ω
3. 1 Ω
4. 12 Ω

20. In an experiment with potentiometer, null point with a cell is found at 240 cm. When the cell is shunted with a resistance 2 Ω, the null point becomes 120 cm internal resistance of cell is :

1. 4 Ω
2. 2 Ω
3. 1 Ω
4. 12 Ω

21. In parallel combination of n cells, we obtain

1. more voltage
2. more current
3. less voltage
4. less current

22. Kirchhoffs first and second laws for electrical circuits are consequences of:

1. conservation of energy
2. conservation of electrical charge and energy respectively
3. conservation of electric charge
4. neither conservation of energy nor electric charge

23. Kirchoff‘s first and second laws in the electricity are the laws respectively of

1. Energy and Momentum conservation
2. Momentum and charge conservation
3. Mass and charge conservation
4. Charge and energy conservation

24. Siemen is the unit of:

1. resistance
2. conductance
3. specific conductance
4. None of these

25. Suppose H1 is the heat generated per second in the filament of a 100 W, 250 V lamp and H2 is the heat generated in the filament of a 200 W, 250 V lamp. Then H1/H2 is equal to:

1. 1
2. 2
3. 2-Jan
4. 4-Jan

26. The charge flowing in a conductor varies with time as: q = αt +1/2 βt² + 16 γt3 Where α, β, γ are positive constants. Then the initial current (l) is given by the condition :

1. l = α
2. l = α²
3. l = α^-1
4. None of these

27. The drift velocity does not depend upon

1. Cross-section of the wire
2. Length of the wire
3. Number of free electrons
4. Magnitude of the current

28. The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then

1. The resistance will be halved and the specific resistance will be doubled
2. The resistance and the specific resistance, will both remain unchanged
3. The resistance will be doubled and the specific resistance will be halved
4. The resistance will be halved and the specific resistance will remain unchanged

29. The example of a non-ohmic resistance is:

1. copper wire
2. fi lament lamp
3. carbon resistor
4. diode

30. The internal resistance of a cell of emf 12 V is 5 x 10^-2C Ω. It is connected across an unknown resistance. Voltage across the cell, when a current of 60 A is drawn from it, is

1. 15 V
2. 12 V
3. 9 V
4. 6 V