Chapter 10 - Electricity

Question 1

What is the test to find out if something is a conductor or an insulator ?

Answer 1

Join it across a bulb and a battery, if the bulb lights its a conductor, if not its an insulator

Question 2

Name 3 good conductors:

Answer 2

Gold , silver , copper , graphite

Question 3

Name 3 insulators

Answer 3

wool, rubber , polythene, wax , glass

Question 4

How does a cell connected to a conductor move electrons ?

Answer 4

the electrons are attracted to the positive end of the cell and are repelled from the negative end of the cell

Question 5

Which way does conventional current flow ?

Answer 5

From positive to negative

Question 6

Which way do electrons flow ?

Answer 6

From negative to positive

Question 7

Draw a circuit symbol for a : switch , cell, battery and a resistor.

Answer 7

Please (page 134)

Question 8

Draw a circuit symbol for a : variable resistor, fuse and a voltmeter

Answer 8

Please (page 134)

Question 9

Draw a circuit symbol for an : ammeter and lamp

Answer 9

Please (page 134)

Question 10

What does the long thin line of the cell represent ?

Answer 10

The positive terminal

Question 11

What happens if a cell is connected in the wrong way in a series circuit ?

Answer 11

It cancels the affect of one other battery E.g. 3 1.5V battery’s connected in series if two are connected properly and one is connected the wrong way the total voltage will be 1.5V

Question 12

What is the unit of charge ?

Answer 12

Coulomb (C)

Question 13

What is the unit of current ?

Answer 13

Ampere (A)

Question 14

How many milliamperes in 1 ampere ?

Answer 14

1000 mA = 1 A

Question 15

How many microamperes in 1 ampere ?

Answer 15

1000000 uA = 1A

Question 16

What is the equation for charge ?

Answer 16

Q = I x t
charge = current x time

Question 17

What are the two conditions for an electric current to flow ?

Answer 17

• no gaps in the circuit

- source of energy so that the charge may move

Question 18

What is the equation for resistance ?

Answer 18

R = V/I

Question 19

What is resistance measured in ?

Answer 19

ohms

Question 20

How do you find the total resistance in a series circuit ?

Answer 20

The resistance is simply the sum of the individual resistances of the resistors

Question 21

How do you find the resistance of two resistors connected in parallel ?

Answer 21

R total = R1 x R2 / R1 + R2

‘product over sum’ formula

Question 22

How do you find the resistance of three or more resistors connected in parallel ?

Answer 22

1 1 1 1
—- = – + – + –
Rtotal R1 R2 R3

Question 23

What happens regarding to current and voltage in series circuits ?

Answer 23

• the current across each resistor is the same

- the sum of the voltages across each resistor is equal to the battery or power supply voltage

Question 24

What happens regarding to current and voltage in parallel circuits ?

Answer 24

• the voltage across each resistor is the same as the voltage provided by the battery
• the sum of the currents in each resistor is equal to the current coming from the battery

Question 25

What are hybrid circuits ?

Answer 25

hybrid circuits contain both series and parallel elements.