Week 4

Question 1

What is the unit for current? (DON’T NEED)

Answer 1

Amps

Question 2

What is the unit for resistance?(DON’T NEED)

Answer 2

Ohms

Question 3

What is the equation for charge?(DON’T NEED)

Answer 3

Q = I x T

Q = Charge flow - Coulombs
I = Current - Amps
T = Time - seconds

Question 4

What is the equation for potential difference?(DON’T NEED)

Answer 4

V = I x R

V = Voltage - Volts
I = Current - Amps
R = Resistance - Ohms

Question 5

What is the practical for investigating resistance?(DON’T NEED)

Answer 5

• Connect battery, ammeter and stripped wire in series.
• Attach the voltmeter in parallel with the crocodile clips
• Attach a crocodile clip at 0 cm.
• 2nd crocodile clip at 10 cm.
• Record the current and the voltage.
• Move 2nd crocodile clip another to 20 cm
• Record current and voltage
• Repeat for different lengths
• Then use the V = I x R to figure out the resistance

Question 6

What are the rules in series circuits?(DON’T NEED)

Answer 6

• Current is the same at any point
• Voltage is shared between components (components with bigger resistance have bigger share of pd)
• Total resistance is the sum of the individual resistors

Question 7

What are the rules in parallel circuits?(DON’T NEED)

Answer 7

• Current shared between branches (branch with less resistance has bigger share of current)
• Voltage is the same everywhere
• Total resistance is smaller than the smallest resistor

Question 8

What is current?(DON’T NEED)

Answer 8

The rate of flow of charge

Question 9

What is potential difference?(DON’T NEED)

Answer 9

The energy transferred per coulomb of charge between two points

Question 10

What is a resistor?(DON’T NEED)

Answer 10

Resistance makes it harder for the current to flow

Question 11

What is a thermistor?(DON’T NEED)

Answer 11

A resistor that decreases resistance as thermal energy increases

Question 12

What is an LDR?(DON’T NEED)

Answer 12

A resistor that decreases resistance as the light intensity increases

Question 13

What equation links current, voltage and power?(DON’T NEED)

Answer 13

P = I x V

P = Power
I = Current
V = Voltage

Question 14

What is the shape of a graph with amps on the y axis and volts on the x axis for a filament lamp?(DON’T NEED)

Answer 14

An ‘S’ shape through the origin

Question 15

What is the shape of a graph with amps on the y axis and volts on the x axis for a diode?(DON’T NEED)

Answer 15

The graph will be drawn in the upper right quadrant as diodes only allow current to flow in one way. Going up

Question 16

What is the shape of a graph with amps on the y axis and volts on the x axis for a resistor?(DON’T NEED)

Answer 16

Linear line going through the origin with a positive correlation. Directly proportional

Question 17

Carry out a practical for I - V characteristics(DON’T NEED)

Answer 17

1) Set up a circuit with a battery connected to a variable resistor with a component (lamp, diode or resistor) with an ammeter all in series. The voltmeter should be in parallel with the component.
2) Vary the resistance so that the voltage and the current changes
3) Take readings from the voltmeter and the ammeter and record the results in a table
4) Swap over the wires connected to the battery, so the direction of the current is reversed.
5) Plot a graph