A breaker may be bad if a circuit running from the breaker panel box has lost power. A process of elimination can determine if a faulty breaker is the problem. Test to see if the breaker has simply been tripped. Firmly move the switch on the breaker from the on position to the off position and then back again.
If more electrical items that are attached to the circuit turn on when the breaker switch is set to the on position, then the problem does not lie with the breaker. However, if more electrical items turn off and stay off when the breaker is moved from the off to the on position, then proceed to the next test.
Remove the wire from the breaker in question, and test the breaker with a voltmeter. If the voltmeter reads that there is a current running through the breaker, then the breaker is not bad. If no voltage registers on the voltmeter, then the breaker needs to be replaced.
If a voltmeter is not available, connect a light bulb to the breaker screw and the ground within the panel. If the light bulb turns on, the breaker is not the problem.
Another test to determine if a breaker is bad involves taking the wire that is hooked into the breaker and connecting it to another working breaker. If the electrical items connected to the wire's circuit turn on, the previous breaker is faulty.