Electrical systems Flashcards
Define resistance
Electrical components put up a force against the flow of electrons.
What is the formula for resistance?
resistance= voltage/current
1/R=1/a+1/b
What is the formula for current?
current=voltage/resistance
What are two dangers of electricity?
Electric shock and electric fires
What are the causes of electric shocks?
One cause of electric shocks are damaged and frayed wires. This happens when the covering around a wire is damaged or worn out. A person touching the bare wire will get an electric shock as current flows through the body. Another cause of electric shock is wet conditions. Although water is not a good conductor, it can conduct electricity when it contains impurities. When a person touches a bare wire with wet hands, a current flows through his body, giving him an electric shock. This is less likely to happen if his hands are dry.
What are the safety features in circuits and appliances?
The safety features are fuses, circuit breakers, mains switch and earth wire.
How do fuses function?
When the current is too large, it melts and breaks the circuit, cutting off the supply of electricity. As a result, the wires and components in the circuit are protected from damage. Once a fuse breaks, it needs to be replaced. A fuse can be found in electrical appliances, electric plugs or fuse box.
How do the mains switch function?
The mains switch is also part of the consumer unit. When there is a fire in the building, a burst water pipe, or if there are lose or broken fires, the mains switch is switched off, so as to switch off the main electrical supply to the whole building.
What are the three wires in an electric plug?
Live wire, neutral wire and earth wire
How does the earth wire function?
If a loose or broken wire touches the metal casing of the kettle, the metal casing is said to be live. When a person touches the metal casing, the electric current flows through that person to the ground. The current can kill a person. With earth wire, most of the current flows through the earth wire to the ground instead of through the person, therefore preventing an electric shock.
What is the formula to calculate power?
Power= current x voltage
What is the formula for energy consumed?
energy consumed= power x time
What is the formula for cost of electrical energy?
cost of electrical energy= units of electrical energy used x cost per unit
