Question

1.A 2000 W toaster operates on a household circuit of 200 V. What is the resistance of the wire the make up the heating element of the toaster?
2.An electronic device is rated at 0.35 W when connected to 150 V. What is the resistance of this device?

Answer 1

P - power measured in watts
E - voltage measured in volts
I - current measured in amperes
R - resistance measured in ohms

$E=IR \\P=IE$

1. P = 2000 W, E = 200 V, R = ?

$P=IE \\2000=I200 \\I=10 \\E=IR \\200=10R \\R=20$

2. P = 0.35 W, E = 150 V, R = ?

$P=IE \\0.35=I150 \\I= \frac{0.35}{150} \\ E=IR \\150=\frac{0.35}{150}R \\R= \frac{150^2}{0.35} \\R= 64285.71$