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;

Power = P = 60W

Time = t = 10 mins = 10 x 60 = 600s

Energy transferred = 60 x 600 = 36000J = 36kJ

Date: 2015-12-24; view: 1117