When current 1 flows through a conductor of resistance R for a time t then heat generated in it is given by
where, V = potential difference applied across the end, of the conductor.
Electric Power
The electrical energy produced or consumed per unit time is called electric power.
or
The rate at which work is done by the source of emf in maintaining the electric current in a circuit is called electric power of the circuit.
Electric Power, P = VI = I2R
= (V2/R)
where, V is the potential difference across the conductor, I is flowing through the conductor and R is the resistance.
Its SI unit is watt (W).
The other units of electric power are kilowatt and horse power.
1 kW = 1000 W
1 HP = 746 W
Electric Energy
The energy supplied by any source in maintaining the current in the electric circuit is called electric energy consumed by the electric circuit.
Its SI unit is joule (J) but another unit is watt-hour. The bigger unit of electric energy is kilowatt hour (kWh). It is known as board of trade (SOT) unit.
1 kilowatt hour = 1000 watt x 1 hour
= 1000 J/s x 3600 s = 3.6 x 106 J
1 Horse power = 746 watt
The electric energy consumed in kWh is given by
The electrical resistance of the wires supplying current is very small, therefore these wire do not heat up when current passes through them.
The electrical resistance of filament of a lamp is very high, therefore it shows more heating effect, when electric current passes through it.
A heater wire must be of high resistivity and of high melting point.
Electric Fuse
An electric fuse is a safety device used for protecting electric circuits bum demaging it due to excess flow of current. It is made of tin-lead alloy (63% tin + 37% lead).
It should have high resistance and low melting point and should be connected in series with the live wire.
Maximum safe current which can be passed through a fuse wire is it dependent of its length. However, it depends on the radius r of wire as
I ∝ r(3/2)
Short Circuiting
When accidentily the live wire comes in contact with nutral wire, resistance of the circuit decreases and a high current flows through circuit. This phenomena is called short circuiting.
Overloading
When a high current flows through the wire which is beyond the ra of wire, then heating of wire takes place. This phenomena is ca overloading.
Rating of Electrical Appliances
The values of power and voltage taken together for an el appliance is called rating of the appliance.
When a 40 W and a 100 W bulbs are connected in series, then 40 W bulb will glow brighter than 100 W bulb.
When a 40 W and a 100 W bulbs are connected in parallel, then 100 W bulb will glow brighter than 40 W bulb.
In series, if any bulb gets fused, then others will not glow.
In parallel, if any one bulb get fused, then others will continue to glow.
All switches should be connected in series with a live wire.
Fusing of Bulb When it is Switched On
Usually filament bulbs get fused when they are switched on. This is because with rise in temperature the resistance of the bulb increases and becomes constant in steady state. So, the power consumped by the bulb (V2R) initially is more than that in steady state and hence the bulb glows more brightly in beginning and may get fused.
Chemical Effect of Electric Current
When a direct current flows through a acidic or basic solution it dissociate into positive and negative ions. This phenomena is called electrolysis and these liquids are called electrolytes.
Some Terms of Electrolysis
Anode The electrode connected to the positive terminal battery is called an anode.
Cathode The electrode connected to the negative terminal of the battery is called a cathode.
Anions The ions carrying negative charge and move towards the anode in electrolysis are called anions.
Cations The ions carrying positive charge and move towards the cathode in electrolysis are called cations.
Voltameter The vessel in which the electrolysis is carried out is called a voltameter
where, V = potential difference applied across the end, of the conductor.
Electric Power
The electrical energy produced or consumed per unit time is called electric power.
or
The rate at which work is done by the source of emf in maintaining the electric current in a circuit is called electric power of the circuit.
Electric Power, P = VI = I2R
= (V2/R)
where, V is the potential difference across the conductor, I is flowing through the conductor and R is the resistance.
Its SI unit is watt (W).
The other units of electric power are kilowatt and horse power.
1 kW = 1000 W
1 HP = 746 W
Electric Energy
The energy supplied by any source in maintaining the current in the electric circuit is called electric energy consumed by the electric circuit.
Its SI unit is joule (J) but another unit is watt-hour. The bigger unit of electric energy is kilowatt hour (kWh). It is known as board of trade (SOT) unit.
1 kilowatt hour = 1000 watt x 1 hour
= 1000 J/s x 3600 s = 3.6 x 106 J
1 Horse power = 746 watt
The electric energy consumed in kWh is given by
The electrical resistance of the wires supplying current is very small, therefore these wire do not heat up when current passes through them.
The electrical resistance of filament of a lamp is very high, therefore it shows more heating effect, when electric current passes through it.
A heater wire must be of high resistivity and of high melting point.
Electric Fuse
An electric fuse is a safety device used for protecting electric circuits bum demaging it due to excess flow of current. It is made of tin-lead alloy (63% tin + 37% lead).
It should have high resistance and low melting point and should be connected in series with the live wire.
Maximum safe current which can be passed through a fuse wire is it dependent of its length. However, it depends on the radius r of wire as
I ∝ r(3/2)
Short Circuiting
When accidentily the live wire comes in contact with nutral wire, resistance of the circuit decreases and a high current flows through circuit. This phenomena is called short circuiting.
Overloading
When a high current flows through the wire which is beyond the ra of wire, then heating of wire takes place. This phenomena is ca overloading.
Rating of Electrical Appliances
The values of power and voltage taken together for an el appliance is called rating of the appliance.
When a 40 W and a 100 W bulbs are connected in series, then 40 W bulb will glow brighter than 100 W bulb.
When a 40 W and a 100 W bulbs are connected in parallel, then 100 W bulb will glow brighter than 40 W bulb.
In series, if any bulb gets fused, then others will not glow.
In parallel, if any one bulb get fused, then others will continue to glow.
All switches should be connected in series with a live wire.
Fusing of Bulb When it is Switched On
Usually filament bulbs get fused when they are switched on. This is because with rise in temperature the resistance of the bulb increases and becomes constant in steady state. So, the power consumped by the bulb (V2R) initially is more than that in steady state and hence the bulb glows more brightly in beginning and may get fused.
Chemical Effect of Electric Current
When a direct current flows through a acidic or basic solution it dissociate into positive and negative ions. This phenomena is called electrolysis and these liquids are called electrolytes.
Some Terms of Electrolysis
Anode The electrode connected to the positive terminal battery is called an anode.
Cathode The electrode connected to the negative terminal of the battery is called a cathode.
Anions The ions carrying negative charge and move towards the anode in electrolysis are called anions.
Cations The ions carrying positive charge and move towards the cathode in electrolysis are called cations.
Voltameter The vessel in which the electrolysis is carried out is called a voltameter
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