A parallel DC circuit has a total current of 4 Amperes and a resistance of. 5 Ohms. If the current is doubled, and the resistance is halved, how many times more is the new power compared to the old power?

The answer is 2 times.

In parallel DC circuit the power (P) can be calculated by using the values of total current (I) and resistance (R):

P = I²R

The old power is:

Po = Io² x Ro

Io = 4 A

Ro = 0.5 ohms (Ω)

So, Po = 4² A x 0.5 Ω = 8 W

The new power is:

Pn = In² x Rn

In = 4 A x 2 = 8 A

Rn = 0.5 Ω : 2 = 0.25 Ω

So, Po = 8² A x 0.25 Ω = 16 W

Pn : Po = 16 W : 8 W = 2

Thus, the new power is 2 x higher than the old power.