When a certain a.c supply is connected to a lamp, it lights with the same brightness as it does with a 12 V d.c battery. Then r.m.s value of the a.c supply ...

When a certain a.c supply is connected to a lamp, it lights with the same brightness as it does with a 12 V d.c battery. Then r.m.s value of the a.c supply is?

Answer Details

The root mean square (rms) value of an alternating current (AC) is the equivalent steady or direct current (DC) value that gives the same energy to a resistor as does the AC. When an AC supply is connected to a lamp, the brightness of the lamp depends on the power being delivered to the lamp. If the lamp lights with the same brightness as it does with a 12 V DC battery, it means that the power being delivered to the lamp in both cases is the same. Therefore, the rms value of the AC supply must be the same as the DC voltage of the battery, which is 12.0 V. Thus, the answer is 12.0 V.