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