如果用9V既”差”電器去”差”個5V既電池有咩問題?

通常可充電池會有一個熱敏電阻以防止過度充電既，當你用9V既"差"電器去"差"個5V既電池時，電池好快發熱，而熱敏電阻發熱時提高電阻值，已達到限制充電電流，但係，如果冇熱敏電阻，你個”差”電器同個5V既電池都會發熱，甚至爆裂，小心為上。

Tremendous amount of heat will be produced and this will burn your battery.

Assume the internal resistance of your 5v battery be 1 ohm, and the 9v charger be of negligible intenal resistance.

When they are connected, by Ohm's Law, the current through the circuit
= (9-5)/1 A = 4 A

The power dissipated at the 5v battery in the form of heat
= 4^2 x 1 W = 16 watts

This amount of heat produced per second certainly will get the battery hot and burn it off.