Recall Facts-circuits 1-30

Question 1

What is current?

Answer 1

It is the rate of flow of electric charge

Question 2

Why are metals good conductors?

Answer 2

Because they have free moving electrons

Question 3

What is the unit for current?

Answer 3

Amps

Question 4

When a voltage is applied, what end do the electrons move to?

Answer 4

It goes from negative to positive

Question 5

What is the main difference between conductors and insulators?

Answer 5

Insulated have less free electrons

Question 6

What is potential difference?

Answer 6

It is another word for voltage. The difference in work done by or on a charge between two points in the circuit.

Question 7

How is an ammeter connected in a circuit

Answer 7

In series (within the loop)

Question 8

How is a voltmeter connected in a circuit?

Answer 8

Parallel to the component being measured

Question 9

How can they be potential difference, but not a current

Answer 9

Incomplete circuit

Question 10

What is resistance

Answer 10

Opposing the flow of charge (current)

Question 11

What causes resistance in a wire

Answer 11

Resistance is caused by the electrons colliding with positive metal ions of the wire

Question 12

State factors that affect the resistance of a wire

Answer 12

Length of wire
Temperature
Thickness of wire
Material of wire

Question 13

What is the job of a variable resistor?

Answer 13

Alter the resistance of the circuit and therefore current and potential difference across different components

Question 14

What is the relationship between potential difference and current for fixed resistance

Answer 14

Has the potential difference increases the current also increases

Question 15

What is the relationship between resistance and current for fix potential difference

Answer 15

As the resistance increases the current decreases

Question 16

What is the equation linking charge flow current and time?

Answer 16

Charge flow (c)=current (A) x time (S)
Q=I x T

Question 17

What is the equation for resistance?

Answer 17

Resistance (ohms)=Voltage (V) / Current (A)

Question 18

State ohms law

Answer 18

Potential difference is directly proportional to the current for a fixed resistor resistor at constant temperature

Question 19

What is meant by directly proportional?

Answer 19

This is a Y=MX graph (straight line through origin) or when one factor doubles, the other factor also doubles

Question 20

Describe the difference between linear and non linear graph

Answer 20

Linear graph-straight line
Non linear graph- not a straight or curves

Question 21

Which of the I-V geaphs are linear

Answer 21

Fixed resistor, resistor at constant temperature

Question 22

Which of the I-V grapgs are non linear

Answer 22

Filament lamp (bulb) and diode

Question 23

Explain the shape of the fixed resistor line

Answer 23

Resistance is constant so straight line and follows ohms law

Question 24

Explain the shape of the filament lamp graph

Answer 24

As potential difference and current increases bulb get hotter and this increases resistance

Question 25

Explain the shape of the diode graph

Answer 25

Very high resistance in reverse direction for no current very low resistance and forward directions for rapid increase in current

Question 26

What is power?

Answer 26

How is the rate of energy transfer or how much energy is transferred in one second or power equals energy divided by time

Question 27

What is power measured in?

Answer 27

Watts

Question 28

What are the equation for power?

Answer 28

Power (W)=(Current) squares (A) x Resistance (ohms)
p=I squared x R

Power (W) = Potential difference (V) x Current (A)
P=V x I

Energy (J)= Power (W) x time (S)
E=Pxt