Physics class 12 chapter 3 Objective Questions

1. An electric heater is connected to the voltage supply. After few seconds, current gets its steady value then its initial current will be

(a) equal to its steady current

(b) slightly higher than its steady current

(c) slightly less than its steady current

(d) zero

Answer: (b) slightly higher than its steady current

2. In the series combination of two or more than two resistances

(a) the current through each resistance is same.

(b) the voltage through each resistance is same.

(c) neither current nor voltage through each re-sistance is same.

(d) both current and voltage through each resis¬tance are same.

Answer: (a) the current through each resistance is same.

3. Combine three resistors 5 Q, 4.5 Q and 3 Q in such a way that the total resistance of this combination is maximum

(a) 12.5 Q

(b) 13.5 Q

(c) 14.5 Q

(d) 16.5 Q

Answer: (a) 12.5 Q

4. In parallel combination of n cells, we obtain

(a) more voltage

(b) more current

(c) less voltage

(d) less current

Answer: (b) more current

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

(a) change in previous direction

(b) not change

(c) change in opposite direction

(d) none of these.

Answer: (b) not change

6. When a metal conductor connected to left gap of a meter bridge is heated, the balancing point

(a) shifts towards right

(b) shifts towards left

(c) remains unchanged

(d) remains at zero

Answer: (a) shifts towards right

7. 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

(a) decrease resistance in the main circuit.

(b) increase resistance in the main circuit.

(c) decrease resistance in series with the cell whose emf is to be measured.

(d) increase resistance in series with the cell whose emf is to be determined.

Answer: (d) increase resistance in series with the cell whose emf is to be determined.

8. AB is a wire of potentiometer with the increase in the value of resistance R, the shift in the balance point J will be

(a) towards B

(b) towards A

(c) remains constant

(d) first towards B then back towards A.

Answer: (a) towards B

9. A charge is moving across a junction, then

(a) momentum will be conserved.

(b) momentum will not be conserved.

(c) at some places momenturii will be conserved and at some other places momentum will not be conserved.

(d) none of these.

Answer: (d) none of these.

10. The I-V characteristics shown in figure represents

(a) ohmic conductors

(b) non-ohmic conductors

(c) insulators

(d) superconductors

Answer: b

11. Which of the following is correct for V-I graph of a good conductor?

(a) ohmic conductors

(b) non-ohmic conductors

(c) insulators

(d) superconductors

Answer: (b) non-ohmic conductors

12. The resistivity of alloy manganin is

(a) Nearly independent of temperature

(b) Increases rapidly with increase in temperature

(c) Decreases with increase in temperature

(d) Increases rapidly with decrease in temperature

Answer: (a) Nearly independent of temperature