Class 7 Physics Electric Current and its Effects Applications ofHeating effect of Current

Applications ofHeating effect of Current

Electrical Fuse andCircuit Breakers

A Fuse or a Circuit Breaker is a device which protects appliances from overcurrent or overload.

  • In the circuit, it is placed after the power source and before the appliance.
  • It has a wire of low resistance and low melting point.
  • In case of excessive current, the wire of the fuse melts resulting in breaking of the circuit. Thus, no current flows through the main appliance, protecting it from damage and possible fire.
  • Some of the causes of excessive current are
    • Short Circuit: can occur due to direct touching of two wires, water seepage inside and electric circuit etc
    • Overload: Connection of many devices into single socket.
    • Excessive current generated from power source.
  • Every Fuse is labeled with the maximum rating (current and voltage it can withstand before breaking).So, appropriate fuse should be used according to the appliance/circuit requirements.
  • Using a lower capacity fuse will result in frequent breaking of circuit. On the other hand, using a higher capacity fuse may not break in slightly excessive current and the appliance may damage.
  • An MCB (Miniature Circuit Breaker) is a switching device which automatically turns off when current exceeds a safe limit.
  • The automatic shutting off is called tripping or trip.
  • MCB does not contain any wire but uses heating effect of current to break the circuit.
  • In case of overload or overcurrent, a fuse gets burnt and needs to be replaced whereas a circuit breaker can be reset (like a normal switch) to resume normal operation.

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