Ex. 2. Complete the extract about current and power calculations using the words in the box

Ex. 1. Complete the word puzzle and find the key-word.

Basic Notions: Electric Current, Voltage and Resistance

Unit 1

Electrical Transport and Power Supply

Учебное пособие для студентов IV курса специальностей Электрический транспорт и Электроснабжение

Electric current is a flow of electrons, forming electric charge. Electric current is measured in amperes or amps (A). Electrons are particles with a negative charge, attached to atoms. When an electric current flows through a conductor, the electrons move from one atom to another. If the number of electrons flowing through a conductor increases then the amperage or ampage (current) increases.

The amount of current (in amps) flowing through a circuit partly depends on the electromotive force (EMF) of the electrical supply. EMF is measured in volts (V) and is called voltage.

The amount of current also depends on electrical resistance. It is a measure (in ohms - Ώ) of how easily current can flow through the conductors and components in a circuit.

Materials with high resistance are called electrical insulators. Materials that are good insulators are used to insulate conductors. An example is plastic insulation around electric wires.

The amount of current required by an electrical appliance or devices depends on the power of the appliance. The power is expressed in watts (W).

1.	ELECTRIC
2.	ELECTRIC
3.	ELECTRIC
4.	ELECTRIC
5.	ELECTRIC
6.	ELECTRIC
7.	ELECTRIC
8.	ELECTRIC

1. another term for amperage

2. provided by a battery, for example

3. measured as a wattage

4. allows current to flow through it

5. has very high electrical resistance

6. carried by moving electrons

7. another term for electrical “device”

8. the consequence of a person touching a live conductor

amps conductor current resistance voltage wattage

components circuit ohms supply volts watts

In electrical calculations, electromotive force is expressed by the letter E, resistance by the letter R, and current by the letter I (which comes from the word “intensity”).

According to Ohm’s Law: I = E/R.

In other words, the (1) … flowing through a (2)….., measured in (3)….., equals the (4)..... of the electrical (5)….., measured in (6)….., divided by the total (7)….., measured in (8) … To work out the value of R, it is necessary to calculate the total resistance of all the (9)….. and connecting lengths of (10)….. that make up the circuit.

Once both the voltage and amperage are known, it is possible to work out the power, measured in (11)….., that will be consumed. Power (P) can be calculated using the equation P = EI. Therefore, (12)….. equals voltage multiplied by amperage.

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