An extension cord is used with an electric weed trimmer that has a resistance of 7.0 Ohms.?

Question

The extension cord is made of copper wire that has a cross-sectional area of 2.70 x 10^-6 m2. The combined length of the two wires in the extension cord is 76 m.

(a) Determine the resistance of the extension cord.

__________ Ohms

(b) The extension cord is plugged into a 60-V socket. What voltage is applied to the trimmer itself?

_________ V

Answer 1

the resistance is calculated using rho*L/A.  Since you can consider both ends of the cord as one resistor because the resistances are in series, you use the given length of two combined wires.  rho is probably given, and is the resistivity of copper.

For the second part, you have a voltage divider with your answer from part (a) and the 7 Ohms of resistance for part B.  So you would have Vsocket*Rtrimmer/(Rtrimmer+Ra).  Hope this helps