Phyiscs Ka2

Question 1

Where are semi conductors found?

Answer 1

On the boundary between metals and non-metals

Question 2

Why is silicone a semi conductor?

Answer 2

Because it doesn’t have energy, they behave like insulator but with no free electrons. When we put in light they release electrons

Question 3

What is a diode?

Answer 3

A diode is made of two pieces of semi-conductor, treated so the electrons will only flow directly across the boundary.

Question 4

What happens to a diode in a circuit?

Answer 4

It allows current to flow easily on the forward direction, but not in the reverse direction

Question 5

The sum of the p.d of the components in a series circuit = ???

Answer 5

The supply p.d (Vs = V1 + V2)

Question 6

In a parallel circuit the p.d across each component = ???

Answer 6

The battery P.d (Vs = V1 = V2)

Question 7

What is the striped wire and where is it?

Answer 7

The earth wire and at the top

Question 8

What is the brown wire and where is it?

Answer 8

The live wire and on the right

Question 9

What is the blue wire and what is its charge?

Answer 9

The neutral wire and on the left

Question 10

What are the pins made of in a plug and why?

Answer 10

Brass because it is a good conductor and it is strong so it doesn’t bend and also won’t rust

Question 11

What is the body of the plug made from and why?

Answer 11

Plastic because it is a good insulator

Question 12

Why does the fuse melt?

Answer 12

When the current is too large so the circuit does not break

Question 13

What does the cable grip in a plug do?

Answer 13

Stops the wire from being pulled out of place

Question 14

What happens to the resistance of a filament lamp as the temperature of the filament increases?

Answer 14

It increases

Question 15

A diode has a very ____ _____ in the reverse direction

Answer 15

High

Question 16

What happens to the resistance of a light dependent resistor as the light intensity increases?

Answer 16

It decreases

Question 17

Explain what happens to the lamp in the thermistor circuit

Answer 17

The brightness of the lamp increases as the current increases and the resistance decreases

Question 18

Explain what must happen to the resistance in the LDR

Answer 18

The resistance decreases as the light intensity increases

Question 19

Explain what must happen to the lamp in the LDR circuit

Answer 19

The brightness will increase as the resistance decreases and the current increases

Question 20

In a series circuit, the ____ is the same value at any point in the circuit

Answer 20

Current

Question 21

In a parallel circuit the _____ of the current in each loop is equal to the _______ _______

Answer 21

Sum, current total

Question 22

In a _____ circuit each loop has the ____ P.d across it

Answer 22

Same

Question 23

What is the equation for power and what is it measured in?

Answer 23

Power= energy / time

Measured in W

Question 24

1W = _____

Answer 24

1J/s

Question 25

What is the equation for power in electricity?

Answer 25

Power = p.d x current

Question 26

What happens if the live in a washing machine is damaged?

Answer 26

The case will become live. The earth wire provides a low resistance path for the current to flow from the live wire

Question 27

What is an alternating current? (A.c)

Answer 27

Repeatedly reverses its direction. If flows one way then the other. It's frequency is the number of cycles it passes through each second

Question 28

How much altering potential difference does a typical power station generate?

Answer 28

25000V

Question 29

When are step up transformers used

Answer 29

At power stations to transfer electricity to the national grid

Question 30

When are step down transformers used?

Answer 30

To supply electricity from the national grid to the consumers

Question 31

Why make the grid potential difference very large?

Answer 31

Much less current is needed to transfer the same amount of power, so the power loss due to the resistance hearing the cables is much reduced. This means the national grid is an efficient way to transfer power

Question 32

When is an oscilloscope used?

Answer 32

To show how an alternating potential difference changes with time

Question 33

The uk mains supply is about ____ volts

Answer 33

230

Question 34

Why does a mains cable have two or three inner cores of copper?

Answer 34

Because it's a good conductor

Question 35

How much potential difference do the step up and step down transformers produce?

Answer 35

123000V

Question 36

What is the national grid?

Answer 36

The system of cables and transformers

Question 37

What happens to the electricity produced when a power station passes through a transformer

Answer 37

The voltage increases (step up transformer)

Question 38

What happens to the electricity when it reaches houses or factories?

Answer 38

It must have the voltage reduced (step down transformer) before it can be used safely

Question 39

Why do we use a high voltage in the cables?

Answer 39

To improve efficiency and reduce the waste heat

Question 40

When a current passes through it has a _____ heating effect. Energy is transferred from _____ to ______.

Answer 40

Heating, electrical, thermal

Question 41

The larger the _____ the lower the ______

Answer 41

Transfer, efficiency

Question 42

If we reduce the _____, by increasing the _____, the transmission system is more _______

Answer 42

Current, voltage, efficiency

Question 43

Power loss in a cable = ???

Answer 43

Current² x resistance

Question 44

The p.d of a battery is the ____ supplied to each _____ of _____ as it passes through the battery

Answer 44

Energy, coulomb, charge

Question 45

What is the equation for charge flow?

Answer 45

Charge flow= current x time

Question 46

What is the equation for energy transferred?

Answer 46

Energy transferred = charge flow x p.d

Question 47

What is the equation for total resistance?

Answer 47

Resistance total= R1 + R2

Question 48

What is the equation for potential difference?

Answer 48

P.d = current x resistance