CURRENT, VOLTAGE AND RESISTANCE PROFESSIONAL ENGLISH IN USE FOR ENGINEERING

 

PROFESSIONAL ENGLISH IN USE FOR ENGINEERING UNIT 43. CURRENT, VOLTAGE AND RESISTANCE

 

A Electric current The photo on the opposite page shows a simple electric circuit (or circuit). A cell provides an electric current (or current). This flows through wires, which conduct the electricity (provide a way for it to travel). The current is used to light a lamp, so, like all circuits, the example includes: ·     an electrical supply – in this case, the cell ·     an electrical conductor (or conductor) – an electrical path – in this case, wires B Voltage and resistance The amount of current (in amps) flowing through a circuit will partly depend on the electromotive force (EMF) of the electrical supply. Electromotive force is measured in volts (V), and is generally called voltage. The voltage depends on the ‘strength’ of the electrical supply. In the diagram above, adding a second cell would supply a higher voltage. C Electrical power The text below, about electrical power, is from a home improvements magazine. The amount of current, in amps, required by an electrical appliance – such as a TV or an electric kettle – depends on the power of the appliance. This number – expressed in watts (W) – will be marked somewhere on the appliance. To calculate the required current, EXERCISES 43.1 Complete the word puzzle and find the word going down the page. Look at A, B and C opposite page to help you. 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 an electrical ‘device’ 8. the consequence of a person touching a live conductor 43.2 Complete the extract about current and power calculations using the words in the box. Look at A, B and C opposite to help you. 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 R, it is necessary to calculate the total resistance of all the (9)_______________ and connecting lengths of (10)_______________ that make up the circuit.

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