Electricity - Senior 3 and 4

Marking and Measuring Instruments

Students will be expected to have a knowledge of and use of the following:

(a) Transformers

(b) Wattmeters

(c) Variable transformers and rheostats.

Instruments

Candidates are expected to know how to use and service the following instruments:

(a) a hydrometer

(b) a magnetic compass.

What an Alternating Current Is

(a) A.C. meters, resistance in A.C. circuits.

(b) A.C. series and parallel connections.

Power Transfer From Energy Sources

E.g. dry cells, from generators through transformers to the consumer.

Transformers

How transformers work as step up and step-down transformers.

(a) Construction of a transformer.

(i) Core Construction

(ii) Laminated core construction.

(b) Auto transformers.

(c) Fault finding in transformers.

Electric Motor (Compound Project to be Explained in Detail)

Construction of simple d.c. motor out of spikes, strip iron, tin sheet, transformer wire, etc.

Motor should operate on a 6V- or 12V- car battery or on a battery of dry cells.

Battery Eliminator

Construction of simple battery eliminator to feed a transistor radio. Type of rectification and smoothing felter to choose according to available materials.

- Preferably this should be an individual project but if materials are short it could be made as a group or even class project.

Electric Bell (Compound Project)

Base; woodwork.

Frame, housing cores, etc.: metalwork.

Bell cup: metal beating.

Winding of coil(s) and wiring up: electricity.

Solenoid Plunger Attraction-Type Meter (Compound Project)

Iron core suspended by means of a coil-spring into a coil wound of transformer wire. The extent to which the plunger is pulled into the core is a measure of the amount of current flowing through it. The core should activate a needle running across a scale.

- Scale should be calibrated experimentally by the student.

- Combined woodwork-metalwork-electrical project

- Base to be made of wood.

- Calibration to be done by pupils experimentally.

Synchronous Motor

Construction of simple synchronous motor with scrap iron and transformer wire.

- Purpose is to demonstrate the principle of synchronous motors as the torque is too weak to drive something.

Household Appliance: Causes of Damage and Repair

(a) Replacement of fuse.

(b) Replacement of element in electric iron.

(c) Replacement of brushes in household appliances with electric motors like vacuum cleaners, mixers, fans, etc.

Checking Automotive Electrical Circuit

(a) Checking fuses.

(b) Checking wires.

(c) Bushes of generator.

(d) Capacitor.

(e) Spark plugs.

(f) Distributor points, cap, rotor.

Measuring Electrical Power and Energy

(a) Measuring power consumed by lamps and household appliances with volt and ammeter (ignoring power factor).

(b) Same measurements with wattmeter (if available). Determination of energy consumed during a certain period (refer to U.E.B. bills and arrange visits to U.E.B. workshops.

Testing House Installation

(a) Testing house installation with circuit tester.

(b) Both self-made panel installation as well as wiring in workshop or classroom should be examined.

Burglar Alarm (Project)

Principle of burglar alarm based on breaking a small current-carrying circuit which holds a relay. The contacts could be placed on a door. If the door opens the circuit is broken and a relay in the circuit operates the alarm which can be the previously constructed bell.

Relay Circuit (Compound Project)

Construction of simple relay and application of the same.

Switch contacts can be made of tin plate.

Semiconductor Sun Relay

Construction of simple circuit which activates a bulb when it gets dark, using a light.