Heat
As electricity flows through the copper wires, it naturally meets resistance. This resistance causes some heat to be released. If the breaker detects an amount of current that would create a dangerous amount of heat, it "trips," or breaks, the circuit.
Excessive Heat
Circuit breakers normally are about as warm as the power inverter in a laptop or other appliances plug. You should also be concerned if it is too warm to the touch. Your breaker box is malfunctioning if you notice a burning smell coming from it or can see any smoke.
Repair
Shut off the power by flipping the breaker's main switch if you suspect a serious problem. Contact a professional to diagnose the circuit breaker's malfunction. If it is becoming excessively hot, it likely needs to be replaced,