Class exercise 1
Find the equivalent resistance of the following circuit.
Class exercise 2
Find the equivalent resistance of the following circuit.
Class exercise 3(P.160#5a)
2
1
4
3
A B
D C
The resistance across AB is:1
4 3 2 9
10
234
1
1
1
R
1
Class exercise 4(P.160#5e)
2
1
4
3
A B
D C
The resistance across AC is:1
4 3
2
21
10
34
1
21
1
R
1
Class exercise 5(P.160#6)
Class exercise 6e.m.f. of the battery = 12 V
100
100
100 X Y
Z
(a) What is the potential difference across X and Z?
(b) What is the potential difference across X and Y?
(c) What is the potential difference across Y and Z?
Class exercise 6e.m.f. of the battery = 12 V
100
100
100 X Y
Z
(d) What is the current flowing out from the battery?(e) What is the current flowing from X to Y?
(f) What is the current flowing from Y to Z via the
upper and lower resistor?
Class exercise 7e.m.f. of the battery = 12 V
120
200
300 X Y
Z
(a) What is the current flowing out from the battery?(b) What is the current flowing from X to Y?
(c) What is the current flowing from Y to Z via the
upper and lower resistor?
Class exercise 8(P.161#9)
Electrical Power
The rating on a lamp is
‘220 V / 1000 W’.
What does it mean?
R
VRIVIP
22
Electrical Power
This means when the lamp is operated normally, that is, when the voltage supplied to the lamp is 220 V, then the lamp consumes electrical energy at a rate of 1000 W.
Under normal state, the electrical energy consumed by this lamp in 1 hour is 1 kWh.
1 kWh = 1000 3600 J = 3600000 J
L,N,E
socket
Green and yellow
blue
brown
Ring circuit
N
E
L
Fuses
Symbol for fuse
Fuse wire is connected with the live wire.
When the current is above the safety limit, the fuse will blow and the live wire is cut off from the mains supply.
Symbol for double insulation
Symbol for double insulation
Class exercise 10
Class exercise 11(P.185#9)
1I 2I
I
Class exercise 12P.185#11)
The lamps are connected in parallel instead of in series for:
(1) The lamps can be operated separately.
(2) If one lamp is damaged, the other
lamps can still function.
Earthing
Earthing
Overloading
Do not overload a universal adaptor.
Damaged wires
Do not touch the damaged wires. Repair the damaged wires.
Damaged wires
Do not pull a plug out from a socket by holding the wire only
Don’t touch the switch with wet hands
Do not operate a switch with wet hands.
Don’t use electric appliances in bathroom
Do not use electric appliances in the bathroom via an extension cable.