P4 Electric Circuits

Question 1

What is current?

Answer 1

The rate of flow of charge

Question 2

What is current measured in?

Answer 2

Amps

Question 3

What the equation for current?

Answer 3

Current = Charge / Time

Question 4

What is charge measured in?

Answer 4

Coulombs (C)

Question 5

What is voltage?

Answer 5

The amount of energy transferred for one coulomb of charge

Question 6

How do you calculate voltage?

Answer 6

Voltage = Energy / Charge

Question 7

What does resistance do?

Answer 7

It slows down the flow of electrical charges in a ciruit.

Question 8

What is resistance measured in?

Answer 8

Ohms (Ω)

Question 9

What are factors which increase resistance?

Answer 9

• Length of the wire
• Higher temperature

Question 10

What factors decrease resistance?

Answer 10

• Type of material (copper has less resistance)
• Diameter (greater diameter has less resistance)

Question 11

What is Ohms’ Law?

Answer 11

When the temperature is constant, voltage and current are directly proportional.
This means the resistance is a constant.

Question 12

What are Ohmic Conductors?

Answer 12

Conductors which follow Ohms Law.

Question 13

What happens when an insulating material loses an electrons?

Answer 13

It becomes positively charged.

Question 14

What happens when an insulating material gains electrons?

Answer 14

It becomes negatively charged.

Question 15

What type of force is between two charged objects?

Answer 15

Non-Contact Force

Question 16

How do you calculate potential difference across a component?

Answer 16

Potential difference = Energy transferred / Charge

Question 17

How do you calculate resitance?

Answer 17

Resistance = potential difference / current

Question 18

In a Filament Lamp as resistance increases …..

Answer 18

temperature increases

Question 19

A thermistor’s resitance decreases ……

Answer 19

if temperature increases

Question 20

An LDR’s resistance decreases ….

Answer 20

if the light intensity increases.

Question 21

How do you calculate resistance using a Filament Lamp graph?

Answer 21

Resistance = 1 / gradient

Question 22

What makes a filament lamp have a high resistance?

Answer 22

• Thin filament with a small diameter
• Some energy is transfered into thermal energy, so cations vibrate more

Question 23

What is the function of a diode?

Answer 23

Diodes let current flow through in only one direction because it has a very high resistance in the opposite direction.

Question 24

When voltage in a diode reaches a certain value…..

Answer 24

current starts to increase

Question 25

What stays the same in each component of a **series** circuit?

Answer 25

Current

Question 26

What is shared between the components of a **series** circuit?

Answer 26

Total potential difference

Question 27

When more bulbs are added to a **series** circuit, why do become dimmer?

Answer 27

Voltage across each bulb decreases and the total resistance of the circuit increases.

Question 28

What is shared between the components of a **parallel** circuit?

Answer 28

Current (*but not the same amounts*)

Question 29

What is equally shared amongst the components of a **parallel** circuit?

Answer 29

Potential Difference

Question 30

Why does adding more resistors in a **parallel** circuit decreases resistance?

Answer 30

The total current through the resistors is increased and the potential difference across them is unchanged

Question 31

What does a cell do?

Answer 31

Pushes electrons around a complete circuit

Question 32

What does a switch do?

Answer 32

It enables you to break and complete a circuit (turn on and off a circuit)

Question 33

What does a bulb do?

Answer 33

Emits light when current flows through it.

Question 34

What does a fixed resistor do?

Answer 34

Limits the current in a circuit.

Question 35

What does a variable resistor do?

Answer 35

It allows the current in a circuit to be varied.

Question 36

What does the thermistor do?

Answer 36

Allows the current depending on the temperature.

Question 37

What does a fuse do?

Answer 37

It is designed to melt or break if the current is too great.

Question 38

What does a diode do?

Answer 38

Allows current through only one direction

Question 39

What does a light emitting diode (LED) do?

Answer 39

Emits light when a current passed through it

Question 40

What does a light dependent resistor (LDR) do?

Answer 40

Decreases in resistance as light intensity increases

Question 41

What does an ammeter do?

Answer 41

It is used to measure electric current (Amps)

Question 42

What does a voltmeter do?

Answer 42

It is used to measure electric potential difference (Voltage)

Question 43

Define electrical current.

Answer 43

The flow of electrical charge.

Question 44

What is potential difference?

Answer 44

Potential difference is the driving force that causes electric charges to flow around a circuit. - measured in Volts (V)

Question 45

**REQUIRED PRACTICAL** - how do you investigate factors affecting resistance of electrical circuits?

Answer 45

1) Using the ruler, measure the distance between the two crocodile clips. This is the “wire length”. 2) Close the switch and record the current and the potential difference 3) Move the claw clips so that the wire length is bigger or smaller. Repeat the measurements of length, current and potential difference. 4) Repeat the experiment for a number of different wire lengths.