Question

A hair dryer draws 12.5 A when plugged into a 120-V line. Assume direct current. (A) What is its resistance? (B) How much charge passes through it in 17 min ?

Answer 1

Concepts and reason

The concept required to solve this problem is ohm’s law and charge.

Initially, calculate the resistance of the hair drier using ohm’s law. Finally, calculate the charge passing through the hair drier using the formula of the charge.

Fundamentals

Resistance is given by,

Here, is the current passing through the drier and is the voltage.

The formula for charge is given by,

Here, is the current passing through the drier and is the time.

(a)

Calculate the resistance as follows:

Substitute for and for in the equation .

Therefore, the resistance is .

(b)

Calculate the charge passing through the hair drier as follows:

Substitute for and for in the equation .

Therefore, the charge passing through the hair drier is .

[Part b]

Part b

Ans: Part a

Therefore, the resistance is .

Part b

Therefore, the charge passing through the hair drier is .