Ch.8.4

Question 1

What is voltage?

—It is a measure of

Answer 1

the amount of energy supplied to the free electrons by a source of electricity such as electric cells.

Question 2

An electric cell with a ________________ ________________ supplies ________________ ________________ to the free electrons in a circuit.

Answer 2

higher voltage, more energy

Question 3

Voltage is related to the ‘________________ ________________’ that makes free electrons flow in a circuit.

Answer 3

electrical push

Question 4

The ________________ the voltage, the ________________ the ‘electrical push’.

Answer 4

higher, greater

Question 5

Why don’t we get an electric shock from touching batteries, but we do from an eel?

• Batteries
• Meanwhile,
• Only

Answer 5

• Batteries have a low voltage/ very small current. -Meanwhile, eels can produce a voltage up to 500 volts.
• Only a high voltage source can easily drive a long current through the human body.

Question 6

We can use a ___________________ to measure voltage.

Answer 6

voltmeter

Question 7

The unit of voltage is ______________ (_____).

Answer 7

volt, V

Question 8

A voltmeter is connected in a _______________ circuit, while an ammeter is connected in a _______________ circuit.

Answer 8

parallel, series

Question 9

What does it mean when a negative voltage is shown on a voltmeter?

Answer 9

It means that the wires are connected to the wrong poles.

Question 10

Describe the relationship between voltage and the size of cells.

Answer 10

Voltage is independent to the size of cells.

Question 11

No. of cells ^^
____________ ^^
____________ ^^
____________ ^^

Answer 11

voltage, current, brightness

Question 12

Why do cells have to be arranged with the negative and positive poles touching each other?

Answer 12

This is because if they are arranged with the same poles facing each other, they will cancel out the electrical push.

Question 13

When several electric cells are connected ________________ in the same direction, the voltage across them is _________________________________________________________.

Answer 13

end-to-end, higher than that of one single cell

Question 14

The total voltage across the connected cells is the _________________________________________________________.

Answer 14

sum of the voltages of all the electric cells

Question 15

The current ________________ when the voltage ________________. The ________________ the voltage, the ________________ the current.

Answer 15

increases, increases, higher, larger

Question 16

Why does the light bulb of a torch become dimmer after being used for a period of time?

Answer 16

This is because when the electric cells in a torch almost run down, their voltages drop and the current decreases.