ELECTROMAGNETISM EXPERIMENTS
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THE PHYSICS SUPERMARKET
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1. Magnetic Fields
Students investigate the magnetic fields around bar magnets and wires. The right hand grip rule is
developed for the field around wires. Students investigate the force on a current carrying wire in a
magnetic field and the right hand slap rule is developed. Two long parallel wires are analysed theoretically. The unit of magnetic field, the Tesla and the origin of the no. 6.242 x 1018 is explained.
2 Bar magnets, Mapping compass, 2-12 V DC Power supply, Solenoid from 'current balance' experiment,
Retort stand, 2 Bossheads and two clamps, Connecting wire, Wire strippers.
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2. Magnetic Field of a Wire
Students use a magnetic compass to determine the relationships between the strength of a long straight
wire's field, the distance from the wire and the current in the wire.
Mapping compass, 4 meter length of thin connecting wire, 2-12 V DC Power supply, 0-5A ammeter, Stand,
Bosshead and clamp, 1 meter ruler, sticky tape brick, rheostat, graph paper, a reversing switch is useful
but not essential. Top
3. Magnetic Field of a Solenoid
Students use a current balance to determine the magnitude of the magnetic field down the centre of an air-cored solenoid. The value is compared with the theoretical value determined from the formula m0nI
Solenoid and current balance kit, 2-12 V DC power supply, 2 rheostats, 2 ammeters 0-5 A, Block of wood
approx. 8 cm x 5 cm x 2 cm. Top
4. The DC Electric Motor
Students analyse the motion of a single current carrying loop free to rotate between the poles of two bar
magnets. The need for a commutator is developed and how why is causes continuous rotation is explained.
Students analyse a three pole electric motor and determine the polarity of the poles as they turn.
Improvement in torque by using three poles is established.
2-12 V DC power supply, 12 V DC motor of the type in electric model racing cars, Mapping compass,
2 leads with banana plugs on their ends. Top
5. Electromagnetic Induction
Students use a magnet, a solenoid and a galvanometer to investigate electromagnetic induction. Magnetic
Flux is defined and ways of changing the flux discussed and investigated.
Bar magnet, Galvanometer 0-50 mA, Large and small matching solenoids with
metal rod, 2-12 V DC power supply, rheostat. Top
6. Time Rate of change in Magnetic Flux
Students use the air core solenoid they used in the experiment Magnetic Field of a Solenoid, a plastic tube with 20 turns of enamelled copper wire wrapped around it, an AC power supply and a CRO. The maximum rate of change in magnetic flux through the copper wire coil is determined when inside the air core solenoid. This is then compared with the maximum value of the induced EMF in the copper wire coil. The direction of the induced field and current is related to the flux change through the coil.
Solenoid used in 'Magnetic field of a solenoid', Plastic pipe 15 cm long and 3 cm diameter with 20
turns, of 0.2 mm diam. enamelled copper wire wrapped around its centre, 2-12 V AC power supply,
Galvanometer, bar magnet and 2 large solenoids used in the experiment 'Electromagnetic Induction'.
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7. AC/DC
The sinusoidal nature of the induced EMF of a rotating coil is established. The formula for the maximum EMF of a generator is developed. The relationship between peak and RMS values of current and EMF is discovered. This relationship is checked by heating water in a calorimeter using a DC supply and then an AC supply set so its output has an RMS value equivalent to the DC supply.
Model generator and cathode ray oscilloscope, 6 V dry cell or four 1.5 V dry cells, 0-12 V DC voltmeter,
Calorimeter, 2-12 V AC power supply, Rheostat, -10 to 110 C thermometer. STop watch, Multimeter with
0-12 AC volt range. Top
8. Transforming Alternating currents
Students use a solenoid set - one large with lots of turns and the other small with fewer turns that fits inside the large one. They use an AC supply to investigate the step up and step down situations.
Large and small matching solenoids with metal rod, 2-12 V AC power supply, 0-20 V AC voltmeter.
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9. Power Transmission
A model transmission system is used consisting of two transformers with transmision wires connected to them. An AC power supply is used to light a globe with the transformers included and excluded from the circuit. It is established that there is a much greater power transfer to the globe when the transformers are included.
Jupiter Scientific Power Transmission Model available from Haines Educational 1717 Dandenong Road
Oakleigh 3166 Victoria Australia Ph. 61 03 5627717.), 2-12 V AC power supply, Multimeter with 0-12 V
AC range and 0-10 A AC range. Top
