Appliance a. the state of having no protection from something harmful
2. mains b. a device that measures and records the quantity, degree, or rate
Equation c. a device or piece of equipment designed to perform a specific task
Exposure d. the glass part of an electric lamp, which gives out light
Bulb e. an electrical circuit system
Meter f. a mathematical statement saying that two amounts or values are equal
B. Adjectives:
1. renewable a. existing or occurring before in time or order
Previous b. relating to science which deals with the physical structure of the earth
Geological c. being moved from one place to another
Nuclear d. being needed for a particular purpose
Transferred e. being not permanently depleted when used
Required f. relating to the energy released when the nuclei are split or combined
C. Verbs:
To multiply a. to reduce the number or quantity of
To fit b. to increase a number in several times
To deplete c. to melt a material with intense heat so as to join it with something else
To fission d. to have the requisite qualities or skills to do something perfectly
To define e. to divide or split into two or more parts
To fuse f. to make clear the nature, scope, or meaning of something
Exercise 2. Match the beginnings of the following sentences with their ends:
Electrical Power
1. Electrical appliances … a. … being equal to 1 joule per second.
2. The power of an electrical appliance is the … b. … rate at which it transforms energy.
3. Power is defined as … c. … transform energy.
4. It is measured in watts (W) with 1 watt … d. … the rate of energy transfer.
Exercise 3. Read the following examples and write one of your own:
Example 1.
An electric heater connected to the 230V mains supply draws a current of 4A. Calculate the power of the electric heater?
Potential Difference = V = 230V
Current = I = 4A
Power = P = ?
Using P = V x I
P = 230 x 4 = 920W
Most electrical appliances have their power and the potential difference of the connecting supply printed on them. With this information we can calculate the required current and the rating of the fuse
required.
Example 2. – Fuse Rating.
An electric kettle has a 2500W on a 230V main supply. What fuse should be fitted in the plug?
Power = P = 2500W
Potential Difference = V = 230V
Current = I = ?
Using P = V x I triangle,
We require I so cover I on the triangle which gives Thus
I = P /
I = 2500 / 230 = 10.87A
Therefore a 13A fuse should be fitted.
Remember: Fuse values are only available in 3A, 5A and 13A values
The energy transferred by an electrical appliance can be determined from the relationship
Energy transferred (joules, J) = Power (watts, W) x Time (seconds, s)
Therefore, if an electric bulb with a power of 60W is on for 10 minutes the energy transferred as heat and light can be calculated as follows;