If the North pales of two magnets are brought close lo each

If the North pales of two magnets are brought close lo each other, the magnets will (A) attract (H) repel (C) both A and B (D) neither A nor B 2. A unit of magnetic field is (A) Coulomb (B) Watt (C) Tesla (D) Joule 3. The charging time of a capacitor in RC circuit increases if (A)resistance is small and capacitance is small (B)resistance is small and capacitance is large (C) resistance is large and capacitance is large (D) resistance is small and capacitance is small 4. If the voltage across a capacitor is doubled, the energy stored in the capacitor (A) halves (B) stays the same (C)doubles (D) quadruples

Solution

1. Same kind of pole repel each other if brought together. (B)

2. Unit of magnetic field is Tesla (C)

3. Charing time is lineraly proportional to time constant RC. If RC increases then charging time shall also increase. Here in the series RC circuit, when we increase both R and C, RC shall also increase and charging time shall also increase. (C)

4. Charged accumulates on capactior is linearly proportional to voltage across capacitor. Energy stored in capacitor is proportional to square of charge accumulated. So doubling the voltage shall cause, energy stored in capacitor to quadruple (four times) (D)