Question

For each conceptual question, state whether its true or false and explain your reasoning.

(a) When 4 identical lightbulbs are connected in parallel to a battery, they will shine brighter (produce more power) than if they were connected in series.

(b) If the distance between two charges is doubled, the force of repulsion or attraction they feel will be halved.

(c) Because the equation for electric potential has distance in the denominator, this means that the electric potential is never zero anywhere (other than “at infinity”), for any situation.

(d) Ohm’s Law is also valid for capacitors if we replace resistance with capacitance in the formula.

Answer 1

a)True

When 4 light bulbs connected in series, resistance of circuit is , current through circuit is , Power produced by each bulb is

When 4 light bulbs are connected in parallel, resistance of circuit is , current through circuit is ,current through each bulb is Power produced by each bulb is

Hence power produced in parallel combination is more (brighter) than series combination.

b) False

Force between two charges is inversely proportional to square of the distance between the charges.

If the distance is doubles, then force becomes one fourth.

c) False

Electric potential at any point depends upon the reference.

Usually, infinity is chosen as the reference. But any point can be chosen as the reference. Only when the reference is at infinity, relationship is true.

Consider a pair of two charges equal in magnitude and opposite in sign,potential at the mid point of line joining the charges is zero.

d)False

Resistance and capacitance are two different physical quantities. So replacing resistance with capacitance in Ohm's law is not valid.