Tag: electric fuse

Answer is D.

When the live wire (high potential) is in contact with the earthed metal case (zero potential) and since there is a potential difference, current flows. As there is little to no resistance in the completed path, the current flow is very large (larger than 4 A melting the fuse). The fuse melts due to high current surge and switches off the circuit.

Answer is D.

The power dissipated is given as P=VI.
In this case, the power of each the bulb is 10 W which uses 220 V supply.
So, the amount of current used is I=P/V = 10/220 = 0.045 A. 
The fuse has a power rating of 5 A. Hence, 5 A / 0.045 A = 111 such bulbs can be connected in parallel with security.
Hence, Mr. Antriksh can use 110 bulbs without any problem. 

Answer is C.

A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, and (usually) enclosed by a non-combustible housing. The fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow. The size and construction of the element is (empirically) determined so that the heat produced for a normal current does not cause the element to attain a high temperature. If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit and the current stops flowing through it.
Hence, the length of the fuse wire is does not matter.

The material used for a fuse wire must have a low melting point so that it melts as soon as excessive current passes through it and thus it can prevent the appliance from damage.

Answer is A.

Fuses are safety devices that are to be built into our electrical system. If there were no fuses and we operated too many appliances on a single circuit, the cable carrying the power for that circuit would get extremely hot, short circuit, and possibly start a fire. To prevent electrical overloads, fuses are designed to trip or blow, stopping the flow of current to the overloaded cable.
The fuse must always be connected to the mains and it must be of correct value. For example, a 15-ampere fuse should trip when the current through it exceeds 15 amperes. A 20-ampere fuse should blow when the current through it exceeds 20 amps.
In this case, the car headlamp is 48 W and the voltage is 12 V.
That is, P = VI, I = P/V = 48/12 = 4 A.
Hence, the fuse of 5 A should be connected to the circuit.

Answer is B.

Fuse boxes contain safety devices called fuses or circuit breakers - MCB (Miniature Circuit Breaker) which are designed to prevent an excess of electric current entering your house by only allowing a certain maximum current to flow in. When the electrical current is too large, an electromagnet attracts a spring loaded switch which breaks the circuit and cuts the power supply. The switch must be reset before any current can flow again.

Answer is A.

The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse F1. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential.

Its length is immaterial for an electric fuse fuse is used to avoid danger due to high current if high current is passed through the fuse it burns and disconnect the power supply the thickness of fuse determines how much current can be pass hence fuse of any length can be used but it's thickness should be proper

Answer is B.

The live wire and neutral wire, coming from the electric pole, enter a box fitted just outside our house which has a main fuse F1. The fuse is connected in series with the live wire. This is done so because it is only the live wire which has a high potential of 220 volts unlike the neutral wire which carries zero potential.

The fuse wire is made of zinc, copper, silver, aluminum, or alloys to provide stable and predictable characteristics. Fuse should be of low resistance and low melting point as per the requirement current rating for overcurrent protection.