Magnetic Effects of Current-3 Flashcards
what is an electric fuse
an eelctric fuse is a safety device that helps save the electrical appliance from burning due to a large amount of current flowing throut it. It is made of a wire of metal having high resisitivity and low meting point like solder. It is connected in series to the circuit with device.
how does a fuse work?
When a large amount of current passes through the fuse, due to heating effect of current, the fuse wire melts and breaks the circuit. Hence preventign the large amount fo current from enetering appliacnce and breaking it.
what is th rating of a fuse
it is the maximum amount of current that can pass through the fse without it melting. It the current exceeds the fuse rating, then fuse wire will melt.
why are there two types of fuses in a domestic circuit?
One type of fuse which is a 5A fuse, is connected to the circuit consisting of low voltage devices like electric bulb, fan etc.
One type of fuse which is 15A fuse is connected to the circuit consisting of high voltage devices like electric geyser, refridgeator etc
what is earthing
one end of the earth wire is connected with the metallic casing of the electrical applieance while the other is connected to the copper plate buried deep inside in the earth.
In case the live wire insulation melts, live wire may touch the metal casing and the current flowing into the electric circuit, we might get an electric chock when handling it.
Instead, this current flowing through the earth wire and into the metal plate deep inside the earth. The earth wire aslo offers least resistance.
The system of connecting the metal casing of the electrical appliance to the copper plate deep inside the earth is called as earthing.
how does fuse help us
TEXTBOOK MOST MOST MOST MOST IMPORTANT
A fuse in a circuit prevents damage to the
appliances and the circuit due to overloading. The use of an electric fuse
prevents the electric circuit and the appliance from a possible damage
by stopping the flow of unduly high electric current. The Joule heating
that takes place in the fuse melts it to break the electric circuit.
define overloading
overloading means the flow of a large amount of current in the circuit beyond the permissible value of current. High amounts of current in the circuit may lead to fire due to overloading.
what causes overloading
(i) Overloading can occur
when the live wire and the neutral wire come into direct contact. (This
occurs when the insulation of wires is damaged or there is a fault in the
appliance.)
ii)Overloading can also occur due to an accidental hike in the supply
voltage.
iii)Sometimes overloading is caused by connecting too many
appliances to a single socket.
iv)whena high power rating device is connected to a low power circuit
what is short circuiting
Shortcircuiting takes place when the live wire and neutral wire come in direct contact. It can happen when the insulation of wire is damaged or there is a fault in appliance.
what happens during a shortcircuiting
when short circuiting occurs, the reisstance of the circuit becomes very low asa result a large amount of current flows through the circuit. A large amount of current produces a large amount of heat and hence the temperature of the circuit reaches a very high value. therefor the circuit catches fire.
what saves the circuit from short circuitign
an elctric fuse is used to save the circuit from damage due to short circuiting. When an electric fuse is connected in series with circuit, the fuse wire will melt due to overheating as soon as short circuiting occurs. This causes the circuit to break and hence the current will not pass through it,
