Electrical Currents

Effects of Electric Current

An electric current can bring about three effects

• heating effect

• magnetic effect

• chemical effect

Multiple Select

Which of the following appliances use the heating effect of an electric current?

Heating effect of an electric current

• When electric current flows through a wire, the wire heats up.

• electrical energy -> heat energy

• For the same amount of current, the greater the resistance of the wire, the greater the amount of heat produced.

Multiple Choice

Between copper and nichrome wire, copper has a lower resistance. Which wire allows more current to pass through?

• copper

• nichrome

Multiple Choice

Between copper and nichrome wire, which one is more likely to be found in the heating element of kettle and why?

• copper has a lower resistance which becomes very hot when current passes through

• nichrome has a higher resistance which becomes very hot when current passes through

Multiple Choice

Between copper and nichrome, which wire is used to make the connecting wires and why?

• Copper, it produces a large amount of heat when current flows through.

• Copper, it prevents a large amount of heat from being produced when current flows through.

• Nichrome, it produces a large amount of heat when current flows through.

• Nichrome, it prevents a large amount of heat from being produced when current flows through.

Multiple Select

The filament of the light bulb is made of tungsten. Select the statements that are true of an electric light bulb.

• Tungsten is likely to have low resistance.

• Tungsten is likely to have high resistance.

• Electrical energy is converted to heat energy, which is in turn converted to light energy.

• Electrical energy is converted to light energy, which is in turn converted to heat energy.

Magnetic effect of an electric current

• View the next video carefully before answering the questions.

Multiple Select

How can you increase the strength of the magnetic effect of an electric current?

• Wrap the wire around a ferromagnetic core (e.g. iron)

• Use a straight wire instead of a coil of wire

• Use a coil of wire instead of a straight wire

What is an electromagnet?

• usually made up of a wire coiled around a piece of iron

• When the current stops flowing, the electromagnet loses its magnetism.

Open Ended

Suggest why magnetic cranes use electromagnets, instead of permanent magnets to separate iron and steel objects from non-magnetic materials.

How electric bell works?

(a) What effect does the current have on the coils of the electromagnet?

(b) (i) What does the electromagnet do the flexible steel spring?

(b) (ii) What does the hammer do?

How electric bell works?

(c) (i) The circuit is then broken. Explain why.

(c) (ii) What then happens to the steel spring?

Other applications of magnetic effect

• vacuum cleaners

• electric fans

• maglev (magnetic levitation) train

Chemical effect of an electric current

• Electric current can be used to bring about chemical changes

• For instance, current can be used to decompose a substance (compound),which is known as electrolysis.

• Electrolysis can be used in electroplating and extraction of metals

• Electroplating is the process of coating / depositing a thin layer of metal on a metallic object

Multiple Choice

The chemical formula of water is H₂O. What do you think are obtained when you perform electrolysis on water?

• water vapour

• ice

• hydrogen (H₂) and oxygen, (O₂)

Multiple Select

Table salt in kitchen is chemically known as sodium chloride.

What do you think are obtained when molten (melted) sodium chloride undergoes electrolysis?

• gaseous sodium chloride

• sodium

• chlorine

• water