An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma.

2. Flow of current
 A charge flows when there is a potential difference
 -- When the ends of an electric conductor are at
different electric potentials, charge flows from one
end to the other
 -- The flow of charge will continue until both ends
reach a common potential
 -- Ex: Difference in water level

3. Electric Current
 Electric Current: The flow of electric charge
-- Solid conductors the electrons can move
around freely carrying the charge
 Electric Current is measured in amperes (A)
amp = 1 coulomb of charge per second
1 coulomb = 6.24 billion electrons

4. Electric Current Cont……
 A current carrying wire does not have a net
electric charge
 While the current is flowing, negative electrons
swarm through the atomic network
 The number of electrons in the wire is equal to the
number of protons
 The number entering is the same as the number
leaving
 The net charge is zero

5. Static Electricity
 Objects can acquire a static electric charge through:
1) Friction (when an object whose electrons are
loosely held rubs against another object)
2) Conduction (when an object with an excess of
electrons touches a neutral object)
3) Induction (a neutral object acquires a charge from
a charged object close by without contact being
made)

6. Resistance
 Resistance: the tendency for a material to
oppose the flow of electrons
 Changes electrical energy into thermal
energy and light
 Ex: lightbulb filament
 Resistance is measured in Ohms (Ω)

7. Conduction
Charging by contact!

8. IV. Control the Flow
 A voltage difference causes the charges to flow
 Flow of charges= current (Amps or A)
 Electrical resistance restricts the movement of
charges
Resistance = current
Pressure = current
(Voltage Difference)

9. Voltage Sources
 Voltage Source: Something that provides a
potential difference
 Dry Cells, Wet Cells and Generators supply energy
that allows charges to move
-- Dry |Wet Cells: Chemical energy converted to
electrical energy
-- Generators: Mechanical energy to electrical
energy

10. Series Circuit
 Current is the same at each point in the circuit
 When another resistor (light bulb) is added in series,
the total resistance increases.
 When resistance increases, current will decrease.
 Decreased current means dimmer light.

11. Electric Resistance
 The amount of charge that flows depends on the
voltage provided by the voltage source
 Electric Resistance: The resistance of a material
to flow of electric current through it: measured in
ohms
-- Depends on the resistance the conductor
provides

12. Electric Resistance
 Thick wires have less resistance than thin wires
 Electric resistance also depends on temperature
-- The greater the jostling about of atoms within
the conductor, the greater resistance the
conductor offers to the flow of charge

13. Ohm`s Law
 Electric Resistance is measured in units called
ohm`s law
Resistance = voltage
Current
Current = voltage
resistance

14. What is the resistance of an electric
frying pan that draws 10 amperes of
current when connected to a 120-
volt circuit?
Resistance = voltage
current
* Measured in ohms

15. Household Electrical Safety
 In a house, many appliances draw current from the same
circuit
 If more appliances are connected to a circuit, more current
will flow through the wires
 More current in wires = more heating in the wires
 More heat causes insulation on wires to melt, which
increases chances of fire
 To protect a house from this, all household circuits have
a:
1. Fuse, or
2. Circuit breaker

16. How much current is drawn by a
lamp that has a resistance of 110
ohms when a voltage of 60 volts is
pressed across it?
Current = voltage
resistance
* Measured in amperes

17. Made By : Sudhanshu
Class : Xth
Roll.No. : 17