Electric Current and its Effects

IMPORTANT TERMS

Ampere             The standard unit of electric current is ampere (A).

Ammeter           A device used to measure electric current.

Electric circuit     The unbroken path through which an electric current flows.

Solenoid            A coil of wire in cylindrical form which when carrying a current acts like a magnet.

Switch               A switch is a device which is used to open or close a circuit. 

Battery              A combination of two or more cells connected in a series is known as battery.

Element             A tightly wound coil of wire.

Electric Fuse      A fuse is a safety device that prevents a sudden surge of current to flow into a device.

 

ELECTRIC CIRCUIT  

 

Electric circuit is the unbroken path through which an electric current flows.

 

The various components of an electric circuit are cell, battery, switch, wire etc. These components of the circuit are represented by standard symbols in a circuit diagram.

 

For an electric circuit to be completed there should be a device or an electrical appliance that uses the current such as an electric bulb. A switch (also called Key) is a device that is used to open or close a circuit. There should be a conducting wire for an electric circuit to be completed. The current flows only when the circuit is complete or closed. If the circuit is unbroken by an insulator in the path of the circuit, the current will not flow.

    

 

Open circuit

The electric circuit in which there is a gap in the connections between the terminals of the cell, wires and the bulb is called an open circuit. If there is an insulator/ break between the path of the circuit, it would be considered as incomplete or open and does not allow the free flow of electricity.

 

Closed circuit

The electric circuit in which there is no gap in the connections between the terminals of the cell, wires and the bulb is called a closed circuit. The current flows only if the circuit is closed.

 

HEATING EFFECT OF ELECTRIC CURRENT

 

When an electric current flows through a wire, the wire gets heated. This is known as the heating effect of the electric current.

 

The heating effect of current is used in various appliances such as electric oven, electric toaster, electric iron etc. These appliances contain elements which heat up when an electric current passes through it. The amount of heat produced in a wire depends on its material, length and thickness.

 

ELECTRIC FUSE

 

An electric fuse is a safety device which prevents the electrical appliances and electrical circuit from electrical hazards during short circuit or overloading. An electric fuse works on the principle of heating effect of electric current. It consists of a metal wire that melts on heating. The wire is made of a material that has a low melting point.

 

The number specified in a fuse indicates the amount of current that can flow through it before it melts. A fuse is always used in an electrical circuit to prevent electrical fire caused due to short circuit or overloading.

 

Short circuiting

Short circuit is caused when positive and negative wires directly come into contact and a large amount of current occurs in the electric circuit. If the current exceeds the safe limit, the wires become overheated and may cause fire. In such case, the fuse wire melts and breaks the circuit.

 

Overloading

Connecting many devices to a single socket causes excessive current in electrical circuit. Hence, it causes overloading in the circuit which can further cause fire. In such situation, if there is a proper fuse in the circuit, it melts and breaks the circuit.

 

Miniature Circuit Breaker

A miniature circuit breaker is an automatic electric switch that protects an electric circuit from damaging during an overload. It performs the same function as a fuse but the switch automatically turns off when current in a circuit exceeds the safe limit. It can be switched on again once the fault is corrected and the circuit becomes complete again.

 

MAGNETIC EFFECT OF ELECTRIC CURRENT

 

An electromagnet consists of a piece of soft iron, with an insulated wire wrapped around it. The iron piece acts like a magnet when a current passes through the wire. The strength of an electromagnet depends on the amount of current passing through it and the number of turns of the wire around the core. An electromagnet is a temporary magnet and loses its magnetism as soon as electric current is switched off.

 

USES OF ELECTROMAGNETS

Electromagnets are used in various fields.

 

• Electromagnets are used in telephones, loudspeakers, cranes electric motors etc.
• Electromagnets are used to separate iron from a garbage dump.
• Electromagnets are also used in electric bells.
• They are used to lift heavy iron objects such as cars.
• They are also used in toys.

 

INTERESTING FACTS

• The first successful electric car was built in 1891 by American inventor William Morrison.
• One power plant can produce enough electricity for 180,000 homes.
• The Earth's core is believed to be a mix or alloy of iron and nickel, giving the Earth its own magnetic field.
• Electricity can be created using water, wind, the sun, and even animal waste.
• Electricity was discovered by the ancient Greeks who demonstrated that rubbing fur against amber led to a mutual attraction between the two materials. However, in 1800 Alessandro Volta produced a steady electrical current.
• Only 10% of the energy used by a traditional light bulb generates actual light. The other 90% of the energy creates heat.
• Compact fluorescent light bulbs (CFLs) use about 80 percent less electricity than conventional bulbs and last up to 12 times longer.
• Electric eels have the ability to generate electricity within their body. They use it for hunting and defense and can send out a shock at 500 volts.