This document is a PowerPoint overview of electricity, focusing on electron theory, current flow, and electrical concepts like electromotive force (emf), voltage, resistance, and power. It explains how electrons, which are negatively charged, move to create electrical current, the significance of potential difference, and the calculations involved in power consumption of various appliances. Specific examples, like the calculation of energy used by appliances, illustrate the application of these concepts in real-life scenarios.

1. Energy & Environment
This PowerPoint is created and developed by :

2. The entire study of electricity is based on the
Electron Theory -
This assumes that all electrical and electronic effects
are due to the movements of electrons from one place
to another
- =
?
Before we work with electricity we must know what
an electron is and what causes it to move -
Lets look first at where we find electrons…in atoms

3. The atom is the building
block of all stuff, or what
scientists call "matter".
Electrons have a negative charge.
- + Protons have a positive charge.
Neutrons are neutral and therefore
have no charge.
What things are made of
atoms?
0

4. - In an Electrically Neutral Atom:
The number of protons=the
number of electrons
+
+ So how many
- +
electrons will there
be?
-
+
It is the movement of
- these electrons
between different
atoms that creates
electricity

5. The flow of electrons is called the
current
Lots of - Attracted to
electrons - +ve
–ve -
The units of current is amps

6. Historic physicists did not know about
atoms and electrons when they created
the rules for electricity.
They knew it was charge that moved but they didn’t
know if it was +ve or –ve. They assumed +ve and that’s
what the rest of electrical rules have been based on
The only way it can work is that the real negatives
flowing in one direction are replaced with imaginary
positives flowing in the other.
This is the way
we will continue -
-ve ve -ve
to think of
current from now
= G Convention
one G
al Current
Electron
+v +v
+ve
Flow e
e

7. For electricity to flow, there has to
be something to push the electrons EMF
along.
This is called an electromotive
force (EMF)
A battery or power outlet creates this
Electromotive force which induces current
in a circuit.
EMF is measured in volts

8. The difference in EMF across
two points is called the
potential difference. (change in
electrical potential energy)
What is the potential difference of
this light bulb?
3volts 5 volts
5 volts-3 volts
=2 volts
So where have the 2 volts gone?
They have been transferred from
- + electrical energy into light
energy.

9. Not all materials give up their
electrons easily.
Remember that metals give up Non
electrons easily whereas non metal-
metals do not give away high
electrons readily resistance
This reluctance to give away
electrons is called resistance. Metal-low
resistance
- - -
- -
- -
- -
-
-- -
- - - -
Low Resistance High Resistance

10. Do these materials high
have high or low
resistance?
high
high
low
low

11. A B
Power=work done -
Work done= moving an electron from one
place to another
Power is measured in Watts
Power =EMF x Current
Watts= Volts x Amps
Current
- - -
EMF - - -
Power =

12. Power =EMF x Current
Watts= Volts x Amps
What is the power of
CFL bulb ?
(CFL stands for compact
filament lamp)
EMF=2 volts
Current=11 amps
What is the power of
filament bulb?
EMF=8 volts
Current=11 amps
Which is better to use and why?

13. Work done in a period of time
Units=Kilowatt Hours (kwh)
Kilowatt Hours (kwh)= power x time
= EMF x current x time
- - -
EMF - - -
Power =

14. A hand grinder in the Vigyan Ashram workshop has a
power rating of 800 watts. It runs for 20 minutes a
session and is used 2 times a day. Calculate the daily
electrical energy that is needed in kwh.
Length of time on a day Convert to hours
=2 times x 20 minutes =40 mins
=40 minutes /day 60 mins/hour
=0.66 hour
Electrical Energy = 800 watts x 0.66 hour
=52.80 watt hours
=0.0528 kilowatt hours

15. The water pump at Vigyan Ashram uses 4.4kwh a day. It
is on for two hours a day. If the EMF of the pump is 230
volts what is the current used?
Electrical energy used Electrical Energy= EMF x current x time
in one hour
=4.4kwh a day Current= Electrical Energy
2 hours a day EMF
= 2.2 kw = 2200
=2200 watts 230
=9.56 amps

16. 1. What direction does conventional current
go? +ve -ve
2. What is resistance? Name a material that has
high resistance and low resistance.
3. What is EMF and what is its units.
4. How can you find the power of an appliance
if you know the EMF and current? X
5. How is electrical energy different from
power?