Electricity from power stations is transmitted to homes through high voltage power lines. Electric potentials as high as 220 000 V AC are used. The electrical potential is decreased to 220 V AC with the help of step-down transformer before it enters the home. A cable containing three color-coded wires enters the home. One wire is red, one s black, and one is green. The red wires are called live wires (or positive). Another wire the the black insulation is called neutral wires (or negative). There is an electrical potential difference of 220 V AC between a red and a black wire. The earth wire, which has insulation of green color , is usually connected to metal plate deep in the earth near the house.
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 heat up sufficiently to bum out. This creates an air gap and no more current flows. A fuse wire is always connected to the live wire so that if excessive current flows through the live wire, then fuse wire melts itself and prevents the appliance from damage.
Illustration : Why a fuse is always connected in series?
Solution : A fuse is always connected in series due to the following given reasons:
At the homes, the electricity first passes through an electric meter. The electric meter records the amount of electric energy used in the home. Then the electricity enters a circuit breaker panel. In some older homes it may enter a fuse panel . In the panel there is a master circuit breaker. The master circuit breaker can be operated manually to cut off the electricity to the entire home. It opens automatically if the current exceeds the rated value. In homes that have a 100 A service, the master circuit breaker will allow up to 100 A to pass before it pops open.
A human body is a good conductor of electricity and we receive shock when the electric current flows through our body. Whenever we use electrical appliances, we must be careful to see that no part of our body comes into direct contact with a wire carrying current.
1. Always use appliances carrying ISI mark.
2. For performing any experiment in electricity use only cells and not the mains supply to your household.
3. Do not put a finger or a metallic wire in the sockets.
In a household electric circuit : | |||
Right Option : B | |||
View Explanation |
Which of the following precaution can be taken while using electricity ? | |||
Right Option : D | |||
View Explanation |
We should not touch switches with wet hands because ____________________ | |||
Right Option : A | |||
View Explanation |
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