This document provides an overview of key concepts related to electricity including: - Definitions of electric current, potential difference, and electromotive force. - Components of an electric circuit and how circuits can be open or closed. - How current and voltage are measured using ammeters and voltmeters. - Ohm's law relating voltage, current, and resistance. - Factors that affect resistance and how resistors can be combined in series or parallel. - Applications of electricity such as heating effects in devices like kettles and light bulbs.

1. ELECRICITY

2.  Def. of Electricity
 Electric Current
 Electric Potential & Potential Difference
 Electromotive Force (emf)
 Electric Circuit and components
 Current and Voltage Measurements
 OHM’s Law
 Factors Affecting Resistance
 Combination of Resistors(Series & Parallel)
 Heating Effect of Electricity and its apps.

3. Electricity is a form of a energy that
can be easily changed to many other
forms

4.  Electric Current is the flow of electric charge
 Measured as the rate of flow of electric
charge
 Denoted by I
 I=Q/t
 SI unit -> Amperes(A)
NOTE-Direction of CONVENTIONAL Current is opposite to direction of flow of
electrons.

5. Electric Potential - Work done in moving a unit charge
from infinity to a point
.∞
A .
Potential Difference – The difference between
potential at two points
.∞
B. A.
Potential difference

6. POTENTIAL DIFFERENCE = Work Done (W)/Charge(Q)
V=W/Q
SI Unit => VOLTS

7. Electromotive force is the same as
voltage.
E.m.f refers to the amount of energy
supplied by the electric source (eg.
battery) to each unit of electric charge
E.m.f is also measured by a voltmeter

10.  To make an electrical appliance work, electricity
must flow through it.
 The path along which the electric current moves
is called the electric circuit.

11. An Electric Circuit is an electrical device that
provides a path for electricity to flow.

12. Circuit diagrams foropen and closed
circuits
Open circuit.
Bulbdoes not light up
whenthe switchis open.
Close circuit.
Bulbwilllightup when
the switchis closed.

13. Symbols

14.  It must be connected in series in the circuit.
 Positive side of ammeter must be connected
nearest to the positive terminal of the battery
(electric cell), and vice versa.

15.  Voltmeters must be connected in parallel to
the circuit.
 The positive side of voltmeter is connected
to the positive terminal of the cell, and vice
versa.

16.  At constant temperature, Current flowing through a
conductor is directly proportional to potential difference
across its ends
 V∝I
 V/I = Constant
= R
 V=IR
 R -> Ressiatance(Ω or ohm)

17.  Fixed resistors have only one resistance
value
 Variable resistors can be adjusted to
change the resistance, example- Rheostat
Fixed Resistors Rheostat

18.  Length of Conductor ->> R∝l
 Cross-sectional Area of conductor ->> R ∝ 1/A
 Nature of material of conductor
 Temperature of conductor
 R∝l/A
ρ – Constant of proportionality called Resistivity
Unit of Resistivity – Ωm
Metals and Alloys have very low resistivity whereas insulators have very
high resistivity
R= ρl/A

19. Thereare 2 ways of joiningresistors together
1. Series
2. Parallel

20. Rs = R1 +R2 + R3

21. 1/Rp = 1/R1 + 1/R2 + 1/R3

22.  When an electric current flows through a wire,
the wire heats up. Electrical energy has been
converted into heat energy.
 The greater the resistance of the wire, the
greater the amount of heat produced. This
heating effect is used in common electrical
appliances.
Iron Kettle

23.  The work done in moving the charge Q through a potential
difference V is VQ
 Therefore, the source must supply energy equal to VQ in
time t.
 So, power input to the circuit by the source is
P = V(Q/t)
P=VI
Energy supplied to the circuit by the source in time t is
P × t
orH= VIt H=I²Rt

24. filament wire produces
heat and light
In a light bulb, the heated filament
which is also a resistance wire,
becomes so hot that light is also
emitted.

25. A kettle uses both copper and nichrome wires.
Copper has low resistance while nichrome has high resistance.
Which material, copper or nichrome, should be used for the heating
element, and for the external wire?
Use copper wire
for the external
wire as it has low
resistance &
produces less heat
Use nichrome wire for the heating
element as it has high resistance&
produces a lot of heat

26. THANK YOU