Unit 13: Electrical Systems Flashcards
What is electric current?
Electric current is the rate of flow of charge.
What is potential difference?
The potential difference across a circuit component is the work done to drive a unit charge through the component.
What is resistance?
The resistance of a component is the ratio of the potential difference across the component to the current through the component.
What is effective resistance?
The effective resistance of a circuit is the total resistance in a circuit due to the resistance of the resistors and any other components with resistance.
What is power?
The power of an electrical component is the amount of electrical energy it converts to other forms of energy in a unit of time (s).
What is the formula for resistance?
resistance (ohms) = potential difference across the component (volt) divided by current flowing through the component (ampere)
Explain the meaning of a 1.5kW rating in an electrical appliance.
1.5 joules of electrical energy is converted to other forms of energy in one second.
How does the earth wire protect the user?
When there is a fault, the metal casing is at high potential. The earth wire provides a low resistance path for the current to travel from metal casing to ground. The low resistance causes a large surge of current through the live wire that will cause the fuse to blow.
What does the fuse protect and how does it protect it?
The fuse protects the heating element. When a current higher than the fuse rating passes through the fuse, it disconnects the appliance from the high potential source.
How does double insulation work as a safety feature?
Doubly insulated appliances are constructed such that the live wire will have an additional layer of insulation from the outer casing.
What are the colours of the earth, neutral and live wire?
The live wire is brown, the neutral wire is blue and the earth wire has green and yellow stripes.
