The resistance of the spiral of one lamp is 20 ohms, and the second is 40 ohms. in which of the lamps will

The resistance of the spiral of one lamp is 20 ohms, and the second is 40 ohms. in which of the lamps will the current do a great job in 10 seconds if each of the lamps is connected to a 220V current source?

Given:

R1 = 20 Ohm – resistance of the first lamp;

R2 = 40 Ohm – resistance of the second lamp;

U = 220 Volts – the voltage of the electrical network to which the lamps are connected;

t = 10 seconds – time span.

It is required to compare A1 and A2 (Joule) – the current in which of the lamps will do the big work for a period of time t.

In the first lamp, the current will perform work equal to:

A1 = W * t = U * I * t = U * U * t / R1 = U ^ 2 * t / R1 =

= 220 ^ 2 * 10/20 = 24200 Joules.

In the second lamp, the current will perform work equal to:

A2 = U ^ 2 * t / R2 = 220 ^ 2 * 10/40 = 12100 Joules.

Since 24200> 12100, the current in the first lamp will do a lot of work.

Answer: in the first lamp, the current will do a great job.