A circuit includes: a first electrical interface including a first pin, a resistor module, an alternating current signal source, a voltage detection module, and a controller. One end of the resistor module is electrically connected to the first pin. The alternating current signal source is electrically connected to the other end of the resistor module, and configured to generate an alternating current detection signal. The voltage detection module is connected to the first pin, and configured to detect a maximum voltage value and a minimum voltage value that are on the first pin within a period of the alternating current detection signal. The controller is separately connected to the alternating current signal source and the voltage detection module, and configured to, when a difference between the maximum voltage value and the minimum voltage value is less than a first threshold, determine that water enters the first electrical interface.