Chapter 11: Practical Electricity Flashcards
Electrical Power and Energy, 3-Pin Plug, Circuit Breakers
What is electrical power defined as?
Rate of electrical work done or electrical energy converted
What equation can be used to calculate electrical power?
Electrical Power (P) = Work Done (W) / Time (T)
OR
Electrical Power (P) = Energy (E) / Time (T)
SI Unit: Watts (W)
How can electrical power be expressed voltage, current and resistance?
P = V x I
P = I^2 x R
P = V^2 / R
How can electrical energy be expressed in voltage, current and resistance?
E = V x I x T
E = I^2 x R x T
E = V^2 / R x T
What is a kilowatt-hour (kWh), and what is it equivalent to?
Unit used for calculating the amount of electrical energy used. One kilowatt-hour (kWh) is equal to the amount of electrical energy used by a 1 kW device for 1 hour
What are the three wires in a three pin plug, and what are their respective colours?
Live Wire (Brown)
Neutral Wire (Blue)
Earth Wire (Yellow / Green)
What is the characteristic of each wire in a three pin plug, and their purpose?
Live Wire: High voltage, supplies power to the electrical appliance
Neutral Wire: Zero voltage, completes the circuit by connecting the electrical appliance back to the power source
Earth Wire: Very low resistance, protects the user from an electrical shock if the appliance becomes faulty
What is the purpose of a fuse and how does it work?
It is a safety device included in an electrical circuit that prevents excessive current flow. The fuse consists of a short piece of wire that becomes hot and melts when the current flowing through it is greater than its rated value (the maximum current)
Which wire are switches and fuses attatched to, and why?
Live Wire. So that the power supply is cut when the switch is opened or when the fuse is blown. If it is fitted to the neutral wire, the electrical appliance will still be at high voltage when the switch is opened or when the fuse is blown. This can cause an electrical shock if the appliance is touched
Which wire can double insulation replace?
Earth Wire
What are circuit breakers?
Safety devices that switch off the electrical supply when there is excessive current
What is the difference between a Miniature Circuit Breaker (MCB) and an Earth Leakage Circuit Breaker (ELCB)?
The Miniature Circuit Breaker (MCB) trips the circuit when excessive current in the circuit is detected, while the Earth Leakage Circuit Breaker (ELCB) trips the circuit when small amount of current is detected leaking from the live wire to the earth wire
