- #1

nokia8650

- 219

- 0

The designer of a heating element for the rear window of a car decides to connect six separate

heating elements together as shown in Figure 2. Each element has a resistance of 6.0Ω and the

unit is connected to a 12V dc supply having zero internal resistance. See: http://img219.imageshack.us/img219/7709/cirrg6.th.jpg [Broken]

In order to calculate the power output of the cicuit, I found the current in one of the resistors (1A), and using P=(I^2)R, found the power output of each resistor to be 6W. 6*6 = 36W for total power output.

I was then asked to compare what would happen if the resistors were in series, which I found Total R = 36 ohms, therefore current = 12/36 = 1/3A. Again, using P=(I^2)R, I found the total power output to be 4 W.

My question is, are the calculations above correct, and if so, how come the output of a supply is varied by the contents of the circuit?

Thanks

heating elements together as shown in Figure 2. Each element has a resistance of 6.0Ω and the

unit is connected to a 12V dc supply having zero internal resistance. See: http://img219.imageshack.us/img219/7709/cirrg6.th.jpg [Broken]

In order to calculate the power output of the cicuit, I found the current in one of the resistors (1A), and using P=(I^2)R, found the power output of each resistor to be 6W. 6*6 = 36W for total power output.

I was then asked to compare what would happen if the resistors were in series, which I found Total R = 36 ohms, therefore current = 12/36 = 1/3A. Again, using P=(I^2)R, I found the total power output to be 4 W.

My question is, are the calculations above correct, and if so, how come the output of a supply is varied by the contents of the circuit?

Thanks

Last edited by a moderator: