Effects of Electric Current
A solenoid-type coil of Tungsten metal is applied in an electric bulb. Give reason.
- The emitting intensity of light by the filament of a bulb depends on the temperature of the filament. It increases with the temperature.
- The melting point of the filament of a bulb is very high so that the filament can be heated to a high temperature by passing a current through it without melting it. This enables us to obtain more light. The melting point of tungsten is very high (3410 degrees Celsius).
- Hence, tungsten metal is applied to make a solenoid-type coil (filament) in an electric bulb.
Copper and aluminum wire is used for electric power transmission. Give reason.
- Aluminum and Copper are superior conductors of electricity.
- Copper and Aluminium have very low resistivity. Hence, when an electric current flows through a copper or aluminum wire, emits comparatively low heat.
- Therefore, copper or aluminum wire is utilized for electric power transmission.
In practice, rather than the joule, the unit k.w./h is indicated for the measurement of electric energy. Give reason.
- If an electric device rated 230V, 5 A is operated for one hour, electric energy used
VIT = 230 volts × 5A × 3600 s
= 4140000 joule.
- If this energy is expressed in kilowatt/hour. It will be 4140000 = 1.15 kw/h (more 3.6 × 10^6 convenient).
- Hence, the unit kilowatt/hour is indicated for the measurement of the electric energy in practice rather than joule.
An alloy as nichrome is applied in the heat-producing electric equipment as iron, electric heater, boiler, toaster, etc., not pure metals are used. Give reason.
- The working of heating devices such as toaster and electric iron is based on the heating effect of electric current and converse the electric energy into heat by passing of electric current through a metallic conductor.
- An alloy such as nichrome has high resistivity. It can be heated to a high temperature without oxidation as compared to pure metals.
- Therefore, the coils in heating devices as a toaster, iron, etc. are made of an alloy as nichrome rather than pure metals.
Equipment as an electric bulb makes use of the heating effect of electric current. Give reason.
- Electrical conductors having higher resistivity are used. A tungsten wire is used in an electric bulb.
- Because of the current, this wire gets heated to nearly 3400 degrees celsius and emits light.
- The hot wire also emits heat to a certain amount.
Buildings catching fire due to short circuits. Give reason.
- The Home electrical connection consists of Live, Neutral, and Earth wires having a potential difference of 220 volts.
- Due to fault in equipment, the Live and Neutral wires come to exposure with each other and a large current flows through it producing heat.
- Any inflammable material that exists around that place can catch fire.
A fuse wire needs as a protective measure in the circuit. Give reason.
- The 'live' and the 'neutral' wires come in touch with each other and a large amount of current flows through it producing heat due to a fault in the equipment.
- The fuse wire melts and breaks the circuit as soon as high current flows in a circuit and any mishap is avoided.
The supply gets shut down many times in the summer season. Give reason.
- Huge electric power is used in the evening due to home lighting, fans, air conditioners, use of electricity in shops, etc.
- As a result, an excessive current is drawn from the transformer supplying the electricity. and if the capacity of the transformer is insufficient, the fuse wire melts, and the supply gets shut down.
