The working of a safety fuse depends upon:
A. Magnetic effect of current
B. Chemical effect of current
C. Magnitude of current
D. Heating effect of current
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → C and D only
A safety fuse is a short piece of wire of low melting point, connected in series with the circuit. When the current rises above its rated value, the heat produced in the wire melts it and breaks the circuit before the appliances or the wiring are damaged.
A. Magnetic effect of current Incorrect. A fuse has no coil or magnet in it; the magnetic effect is what works an electric bell, a relay or an electric motor.
B. Chemical effect of current Incorrect. The chemical effect is used in electrolysis and electroplating; nothing in a fuse wire changes chemically.
C. Magnitude of current Correct. The fuse blows only when the current exceeds its rating. The heat produced, \(H=I^2Rt\), grows with the square of the current, so a fuse rated 5 A carries 5 A safely and melts at a larger current.
D. Heating effect of current Correct. The fuse wire melts because of the heat produced by the current flowing through it (Joule heating).