Chapter 9

Question 1

What do we mean when we say the components are connected in series?

Answer 1

Components are connected end-to-end or one after the other.

Question 2

What do series mean in series circuits?

Answer 2

All the Components are connected end-to-end or one after the other.

Question 3

How many pathes are there for current to flow in a parallel circuit?

Answer 3

In a parallel circuit, there is more than one path for the current to flow.

Question 4

What are branches?

Answer 4

The paths where the current can flow.

Question 5

Explain the name parallel that comes from the circuit diagram.

Answer 5

because the branches are drawn using parallel lines.

Question 6

The components in each of the branches in parallel circuits are sometimes said to be____

Answer 6

connected in parallel

Question 7

What happens to the current at the branch in a parallel circuit.

Answer 7

The current is divided.

Question 8

If two lamps are the same in a parallel circuit, what happens to the current?

Answer 8

The current will be divided equally between them.

Question 9

When the current comes to the other side where the branches join again, what happens?

Answer 9

The current combines again.

Question 10

What is the rule for parallel circuits?

Answer 10

The current through the cell is equal to the total of the current in all the branches.

Question 11

in a parallel circuit, the ammeter on the branch of the cell displays a reading of 5.5 A

The circuit has three parallel branches, not including the first one where the cell is on.

The first branch has a reading of X, second 3.0 A and third 1.5A

calculate the current of the first branch.

Answer 11

X + 3.0 + 1.5 = 5.5
X = 5.5 - 3.0 - 1.5
X= 1.0

Question 12

What are the advantages of parallel circuits?

Answer 12

-The current through a branch can keep flowing even if the current stops flowing in the other branches.

-Components in the same circuit can be switched on and off independently.

-If a component in one branch stops working, the other branches are not affected

Question 13

A circuit has two branches, Each branch has a lamp and a switch.

When the first branch’s switch is closed, what will happen?And why?

Answer 13

The first branch’s lamp will light and the second branch is not affected because it is on a different branch.

Question 14

A circuit has two branches, Each branch has a lamp and a switch.

If both lamps on both branch are switched on and the first branch’s lamp is not working. What happens to the second branch?

Answer 14

It will not be affected.

Question 15

Can components in a parallel circuit be switched on and off separately? How?

Answer 15

Yes, it can. By having switches on each branch.

Question 16

can components in a parallel circuit be all switched on or off together? How?

Answer 16

Yes it can, if the switch is between the cell and the branches.

Question 17

In a parallel circuit with a switch between the cell and the branches, also with switches and lamps in each branches.

What must happen for any lamp to light in the circuit.

Answer 17

The switch between the cell and the branches must be closed, if not, no lamps can be lighted even if separate switches are closed.

Question 18

In a parallel circuit with a switch between the cell and the branches, also with switches and lamps in each branches.

If all the lamps are off but switches on the branches are closed, what will happen?

Answer 18

The lamps are still off.

Question 19

In a parallel circuit with a switch between the cell and the branches, also with switches and lamps in each branches.

If all the lamps are off but switches on the branches are closed, and the switch between the cell and the branch are closed, what will happen?

Answer 19

All the lamps will light together.

Question 20

What is voltage?

Answer 20

Voltage is linked to the electrical energy in a circuit.

Question 21

What is voltage measured in?

Answer 21

Voltage is measured in units called volts.

Question 22

What is the symbol for volts (measure of voltage)

Answer 22

V

Question 23

Voltage is not the same as energy.

True or False?

Answer 23

True

Question 24

Voltage is linked to energy.

True or False?

Answer 24

True

Question 25

What is a battery?

Answer 25

two or more cells connected in a series.

Question 26

What do the sockets found on the walls of building supply?

Answer 26

They supply a mains voltage.

Question 27

Sockets found on the walls of buildings supply a mains voltage. What does Mains in this context mean?

Answer 27

Mains in this context means an electrical supply that comes from a power station or generator of some kind.

Question 28

What components can be referred as a supply?

Answer 28

battery,cell , a power supply or the mains.

Question 29

The lamps used in schools for electrical experiments are often rated at 3V or 6V. What does the rating tell us?

Answer 29

The rating tells us the maximum voltage that can be used.

Question 30

What is voltage linked to?

Answer 30

Voltage is linked to the energy changed by components in a circuit.

Question 31

Give an example of voltage being linked to the energy changed by components in a circuit.

Answer 31

Lamps change electrical energy into light and thermal energy.

Question 32

How is voltage measured?

Answer 32

using a voltmeter.

Question 33

Draw the circuit symbol for a voltmeter.

Answer 33

pg 309

Question 34

Explain the difference between an ammeter and voltmeter.

Answer 34

An ammeter measures the current flowing through a component, so the ammeter is connected in series with the component. While the voltmeter measures the energy difference either side of the component. So the voltmeter is connected in parallel with the component.

Question 35

Draw a circuit diagram with a cell, ammeter, switch, lamp and voltmeter

Answer 35

pg 310

Question 36

Why the energy changed by the components in a circuit must be equal to the energy supplied by the cell, battery or power supply?

Answer 36

Energy is always conserved

Question 37

Describe the relationship with voltages across each component in a series circuit and the voltage of the supply

Answer 37

Voltages across each component in a series circuit must add up to the voltage of the supply.

Question 38

Draw a circuit diagram with 3 voltmeter, 2 cells , 1 lamp and 1 buzzer.

Answer 38

pg 310

Question 39

The voltage from the supply in a series circuit is shared between each of the components. True or false?

Answer 39

True

Question 40

What causes the components to get a smaller share of the voltage.

Answer 40

Adding more components such as lamps or buzzers to the series circuit.

Question 41

What causes the current to decrease in a series circuit.

Answer 41

Adding more components.

Question 42

As more components are added, it becomes more difficult for the power supply to do what?

Answer 42

To push the electrons around the circuit.

Question 43

How to increase the voltage of the supply in a series circuit?

Answer 43

By adding more cells

Question 44

State what effect of increasing the number of cells in the same series circuit.

Answer 44

-increase the current in the circuit -increase the voltage across each component

Question 45

Draw a parallel circuit with 2 cells, 2 lamp and label the voltage

Answer 45

pg 312

Question 46

What is the difference between current and voltage in a parallel circuit.

Answer 46

Current can flow in different paths and be different in the branches of a parallel circuit. The voltage in all branches of a parallel circuit is the same.

Question 47

What happens to the current through the cell when more branches are added to a parallel circuit.And Why?

Answer 47

The current through the cell increases because more branches gives more paths for the current to flow through.

Question 48

More branches increases the current through the cell. More components in the branch makes it harder for current to flow in that branch. Are the two statement above true or false?

Answer 48

TRUE

Question 49

Adding cells to a parallel circuit increases the supply voltage so it also:

Answer 49

-increases the voltage across each branch -increases the current through the cell -increases the current through each branch

Question 50

What is resistance?

Answer 50

Resistance is a measure of how easy or difficult it is for electrons to move through a material.

Question 51

Do copper have high or low resistance?

Answer 51

low

Question 52

Do plastics have high or low resistance?

Answer 52

high

Question 53

What is the unit resistance is measured in?

Answer 53

ohms

Question 54

What is the symbol of Ohms

Answer 54

Greek letter omega (Ω)

Question 55

a 100m length of copper wire can have a resistance of 0.5-1.0Ω true or false?

Answer 55

true

Question 56

A 1 cm length of plastics have a resistance of over 1 trillion Ω true of false?

Answer 56

true

Question 57

What is a filament?

Answer 57

A small wire with high resistance that can be found inside some lamps.

Question 58

Where can filament be found?

Answer 58

Inside some lamps.

Question 59

How do filaments work?

Answer 59

Current flows through the filament, thermal energy is transferred. There is so much thermal energy that the filament glows and emits light.

Question 60

The greater the resistance in a circuit, the smaller_____

Answer 60

The greater the resistance in a circuit, the smaller the current in the circuit.

Question 61

Who was the scientist that studied resistance?

Answer 61

Georg Simon Ohm

Question 62

What is the formula for Ohm's law?

Answer 62

voltage= current x resistance

Question 63

What is a resistor?

Answer 63

A resistor is a type of electrical component designed to have a known resistance.

Question 64

Draw the circuit symbol for a resistor.

Answer 64

pg 321

Question 65

Many resistors, have coloured bands. What is it purposed for?

Answer 65

The colours form a code to show the resistance value in ohms.

Question 66

What is a variable resistor?

Answer 66

A component that is used to change resistance.

Question 67

Draw the symbol of a variable resistor

Answer 67

pg 326

Question 68

What can variable resistor be used for in a circuit?

Answer 68

To control the brightness of a lamp.

Question 69

What are application examples that variable resistor can be useful it?

Answer 69

In dimmer switch for a lamp or in the volume control of a music player.

Question 70

What happens to the current when the resistance of the variable resistor is increased?

Answer 70

The current in the circuit decreases.

Question 71

Explain the relationship with the light inside the fridge and a circuit.

Answer 71

When the door is open, the switch is closed and when the door is closed, the switch is open.

Question 72

Give an example of how circuits can be used for a car.

Answer 72

A buzzer in the car make a warning sound if something is done incorrectly. Buzzer makes a sound when the driver opens the door while the headlamps are switched on. The door of the car controls the switch for the buzzer, but the buzzer should only operate when the headlamps are on.

Question 73

Give an example of how a lamp with low voltage rating is required in a circuit with a battery with higher voltage. Sketch out a diagram for your example aswell.

Answer 73

A 6 V lamp can be operated using a 12 V battery. Two resistors of equal resistance are connected in a series with a battery. The battery voltage will be shared equally across each other. A 6 V can then be safely connected in a parallel with one of the resistors. The lamp with receive a 6 V supply and work. Diagram:pg 328

Question 74

A buzzer in the car make a warning sound if something is done incorrectly. Buzzer makes a sound when the driver opens the door while the headlamps are switched on. The door of the car controls the switch for the buzzer, but the buzzer should only operate when the headlamps are on. Draw a circuit diagram for the scenario above

Answer 74

pg 327