Question

A friend returns to the United States from Europe with a 960-W coffeemaker, designed to operate from a 240-V line. a. What can she do to operate it at the USA-standard 120 V? b. What current will the coffeemaker draw from the 120-V line? c. What is the resistance of the coffeemaker? (The voltages are rms values.) ??

Answer 1

a. To use the coffeemaker, the friend should have to use a step down transformer that has the power to raise voltage

b. The current from the 120 V is 8 A

c. The resistance of coffeemaker is given as 60 Ohms

How to solve for the current

To operate a 960-W coffeemaker designed for 240 V in the USA (where the standard voltage is 120 V), she needs a step-up transformer that can increase the voltage from 120 V to 240 V.

solving for current

Formula for power is

`\[ P = VI \]`

Here we have V = voltage and I is the current

then we make I the subject of the formula

`\[ I = (P)/(V) \]`

from the question,

P = 960 W

V = 120 V

`\[ I = (960)/(120) \]`

I = 8 amperes

c. solving for resistance

Formula for the resistance is

`\[ P = (V^2)/(R) \]`

Make R the subject of the equation

`\[ R = (V^2)/(P) \]`

substitute 240 and 960 into the equation

`\[ R = (240^2)/(960) \]`

R = 60 ohms

In summary the solutions are:

b. The coffeemaker will draw a current of 8 amperes from the 120-V line.

c. The resistance of the coffeemaker is 60 ohms.