UNIT 3 Effects of an electric current
In this unit you will learn about: • the heating effects of an electric current • fuses and short circuits • the magnetic effects of an electric current • the chemical effects of an electric current in solutions.
LET US CHECK
✔ Resistors slow down the flow of current. ✔ Electrical energy can be changed to other forms of energy.
Electric current can have different effects in a circuit. The effects of the current are as a result of energy changes that take place and change the electrical energy into other forms of energy.
Heating effect of electric current
When an electric current flows through a wire, the wire may start to warm up. The wire resists the current. Think of electric fires and the element on the stove. They get a red glow. When the current flows through the thin wire (filament) of a light bulb, it glows white-hot. This is because the thin wire resists the flow of current.
When the electrons pass through a wire, some of their electrical energy is given to the particles or atoms in the wire. The atoms in the wire start to vibrate more and the wire gets hotter as more heat energy is transferred to the atoms. The greater the resistance of the filament, the more energy is transferred to the atoms. This increases the intensity of light or heat that the filament emits.
Practical activity 1
Group work AIM
Caution
Take care that you do not burn your fingers, as the nichrome wire can get very hot.
In this activity you will investigate heating water with a current and resistance wire.
HYPOTHESIS Electric current provides heat.
Investigate the heating effect of a current using a resistance wire
112 Topic 2 Energy transfer in electrical systems
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