what is the resistance?

Question

The power in an electric circuit varies inversely with the resistance. If the power is 1,200watts when the resistance is 12ohms, find the resistance when the power is 2,400watts.
The resistance is

Answer 1

Formulas to know:

 

E = I x R (voltage = current times resistance)

 

This also means that

 

I = E/R   (current = voltage/resistance)

R = E/I   (Resistance = voltage/current)

 

Power is voltage times current - and sometimes you can substitute for voltage or current if you have resistance.

 

What you have:

power = 1200 watts

resistance = 12 ohms

 

power = E²/R, so in the first equation 1200=E²/12 or 14400 = E² so E = 120 volts.

If the volts stay the same, and the power is 2400 watts, then solve for R in :

2400 = 120²/R