Electricity and Magnetism (10)

Ohm’s Law; concepts of emf, potential difference, resistance; resistances in series and parallel, internal resistance.

Electrical power and energy.

Household circuits - main circuit; switches; fuses; earthing; safety precautions; three-pin plugs; colour coding of wires

Magnetic effect of a current; electromagnetic induction (elementary); transformer.

The diagram below shows a loop of wire carrying current I:
How does an increase in the temperature affect the specific resistance
A magnet kept at the centre of two coils A and B is moved to and fro
Calculate the effective resistance across AB
State two ways to increase the speed of rotation of a D.C. motor
Write one advantage of connecting electrical appliances in parallel
What characteristics should a fuse wire have
Which wire in a power circuit is connected to the metallic body
The diagram below shows a dual control switch circuit
Draw a neat labeled diagram of an A.C. generator
Why is it not advisable to use a piece of copper wire as fuse wire
Calculate the total resistance across AB
What are superconductors
The diagram shows a circuit with the key k open
The diagram below shows a magnetic needle
When a current carrying conductor is placed in a magnetic field
The diagram below shows the core of a transformer and its input
Calculate the current drawn by an appliance rated 110 W, 220 V
Name a substance whose resistance decreases with the increase in temperature
Draw a neat labeled diagram of a d.c. motor
You have three resistors of values 2Ω, 3Ω and 5Ω
How is the e.m.f. across primary and secondary coils of a transformer
The diagram shows three resistors connected across a cell of emf 1.8 V
Identify the following wires used in a household circuit
What are isobars
State any two advantages of electromagnets over permanent magnets
A fuse is rated 8A. Can it be used with an electrical appliance rated 5 KW, 200 V? Give a reason.
Find the equivalent resistance between A and B
An electric iron is rated 220V, 2kW
An electric bulb of resistance 500Ω, draws a current of 0.4A
State two causes of energy loss in a transformer
State two characteristics of a good thermion emitter
State two factors upon which the rate of emission of thermions depends
The colour code of the wire connected to the metallic body
Draw the diagram of a dual control switch when the appliance is switched ON
Which particles are responsible for current in conductors
To which wire of a cable in a power circuit
To which wire should the fuse be connected
Explain the meaning of the statement current rating of a fuse is 5A
In the transmission of power, the voltage of power generated at the generating stations
State three factors on which the rate of emission of electrons
What are free electrons
Calculate the quantity of heat produced in a 20 Ω resistor carrying
Which coil of a step up transformer is made thicker and why
Name the transformer used in the power transmitting station
The V-I graph for a series combination and for a parallel combination of two resistors
A music system draws a current of 400 mA when connected to a 12 V battery
A battery of e.m.f. 12V and internal resistance 2 Ω is connected with two resistors