# A 2.2 kilo ohm resistor in a stereo system dissipates 42mW of power. What is the voltage across the resistor?

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### 2 Answers

When current is passed through a resistor there is a dissipation of power. The power dissipated if a current I is passed through a resistor with resistance R is I^2*R

In the problem the resistance of the stereo system is given as 2.2*10^3 ohm and the power dissipated is 42 mW.

=> I^2*(2.2*10^3) = 42*10^-3

=> I = sqrt(42*10^-3/(2.2*10^3))

=> I = sqrt(1.909*10^-5)

=> I = 4.36*10^-3

The voltage across a resistor R that makes a current I pass through it is given by V = I*R

This gives the voltage across the resistor as 4.36*10^-3*2.2*10^3 = 9.6 V

**The voltage across the resistor is 9.6 V**

Resistance = R = 2.2 Kilo ohm = 2200 ohm

Power consumed = P = 42mW = 0.042 W

If current = I

P = I*V ......Power Equation

V = I*R ......Ohm's Law => I = V/R

P = V/R * V = V^2/R

V^2 = P*R

V^2 = 0.042*2200 = 924

V = 30.4 volt

**Voltage** accross the resistor = **30.4 volt**