Question

A battery is replaced with one of lower emf. State and explain how the resistance of the lamps would have to change in order to achieve the same brightness.

Answer 1

Power is the main factor for brightness of the lamp.

Now, power = i^2×R , where i = current and R = resistance of the bulb.

When we replaced the battery with lower emf one, then the circuit current (i) will decrease. Now to achieve same brightness (i.e constant power) , resistance (R) value should be increased.

Answer: Resistance should be increase