Many electrical appliances are designed to work at a particular rated current. Passage of current greater than the rated current will damage the appliance. To prevent electric appliances from getting damaged from an excessive flow of current, a safety device called a fuse is used. A fuse is a safety device which is used to control the current in an electric circuit. It is connected in series with the mains supply. A fuse consists of an alloy of lead and tin which has appropriate melting point. Characteristics of a Fuse: It has a short length wire with a low melting point. The fuse wire is made an alloy containing equal amounts of lead and tin. It melts at about . Electric fuse consists of a solid porcelain grip with two copper clamps. A fuse wire is fixed between the two copper clamps. Principle of an Fuse: The electric fuse works on the principle of heating effect of current. The amount of heating caused depends on the amount of current. An electric fuse consists of a thin wire usually placed inside a glass or ceramic cartridge. The wire is made of a material that melts easily when heated. Working of a Fuse: A wire becomes heated when electric current passes through it. Wires made up of some special material that melts quickly and break when large electric currents are passed through them. Fuses of different kinds are used for different purposes. Different fuse wires can have different thickness. Thicker wires can withstand more electric current. There is a maximum limit on the current which can pass through an appliance or circuit. If by accident the current exceeds the limits, this excess current will pass through the fuse wire and melt it. Tthe circuit is broken. This will stop the passage of the current and the appliance is saved.
When the current flowing through the circuit exceeds the safe limit, the temperature of the fuse wire increases melts and breaks the circuit. It is required to rate the fuses for different current values such as 1 A, 2 A 5 A, 10 A, 15 A, etc. According to the devices used in the circuit we can calculate the amount of current that should allowed to flow through the circuit. A fuse with a rating little more than this value is used in series with the circuit to prevent the damaging of the devices. Fuses and Circuit Breakers: A fuse is a safety device that acts as a switch. Fuses are connected into the circuit close to the source. As a result all the current flowing in the circuit passes through the fuse. When too much current flows, the fuse heats up sufficiently to bum out. This creates an air gap and no more current flows. Illustration: An electrician puts a fuse of rating 5 A in that part of domestic electrical circuit in which an electric heater of rating 1.5 kW, happen in this case and why ? Solution: According to the question p=1.5 kW W, V = 220 V The current drawn by heater can be calculated using the formula
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When a fuse is rated 8A, it means __________________ | |||
Right Option : D | |||
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An electric fuse is based on | |||
Right Option : A | |||
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Fuse of ___________________________ | |||
Right Option : B | |||
View Explanation |
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