Physics

A lightning bolt hits the ground carrying a current of 3 × 10⁴ A. If the strike lasts 50 ms, how much charge enters the ground?

A resistor has a current through it of 5 A. If the EMF across the resistor is 10 V, what is the resistance of this resistor?

Two resistors are made of the same material, one twice as long as the other. If the current through the shorter resistor is 5 A, what is the current through the longer resistor if they both have the same potential difference?

A hair dryer operates at 120 V (the voltage produced by a household outlet), and outputs 1200 W of energy. For this problem, treat the hair dryer as a single resistor. 

(a) At what current does the hair dryer operate?
(b) What is the resistance of the hair dryer?

An incandescent lightbulb produces 100 W of light. If this lightbulb operates at 25% efficiency (meaning that out of all the power it generates, only 25% is released as light), what resistance must the lightbulb have if it operates at 120 V?

What is the equivalent resistance of the following combination of resistors?

What is the equivalent resistance of the following combination of resistors?

If every resistor below has resistance R, what is the equivalent resistance of the combination, in terms of R?

What is current and voltage across each resistor below?

What is the voltage of the battery below?

For the circuit below, find the current through each of the 3 branches.

For the circuit below, calculate 

(a) the voltage V₁ shown, and 

(b) the current through the 6-Ohm resistor.

For the circuit below, calculate the voltage across the 100-Ohm resistor.