P4

Question 1

What is the unit for charge?

Answer 1

coulombs (C)

Question 2

charge flow=

Answer 2

current x time
Q= I x t

Question 3

What’s the equation linking charge flow, potential difference and energy transferred?

Answer 3

Energy transferred = charge flow x potential difference
E = Q x V

Question 4

current:

Answer 4

the rate of flow of electrical charge

Question 5

potential difference:

Answer 5

the energy transferred to a component by each coulomb of charge that passes through it

Question 6

the greater the ____ of a component, the smaller the ___ for a given potential difference across the component

Answer 6

• resistance
• current

Question 7

An electric current flows when _______. The moving electrons can ______. This makes it more difficult for the current to flow, and causes ____. The longer the wire, the _______ and so ____

Answer 7

• electrons move through a conductor, such as a metal wire
• collide with the ions in the metal
• resistance
• more collisions
• higher resistance

Question 8

Describe the relationship between resistance and current

Answer 8

as resistance increases, current increases

Question 9

Describe and explain the relationship between resistance and temperature

Answer 9

as resistance increases, temperature increases

the ions in the metal filament vibrate more as temperature increases, so they resist the passage of electrons more

Question 10

in a series circuit (4)

Answer 10

• current is the same through each component
• the total potential difference of the power supply is shared between components
• the total resistance of two components is the sum of of the resistance of each component
• R total = R1 + R2

Question 11

in a parallel circuit (3)

Answer 11

• the potential difference across each component is the same
• the total current through the whole circuit is the sum of the currents through the separate components
• total resistance of two resistors is less than the resistance of the smallest individual resistor

Question 12

Describe the relation between resistance of an LDR and light intensity

Answer 12

• as light intensity increases, resistance decreases

Question 13

What are LDRs used in?

Answer 13

turning on streetlights

Question 14

Describe the relation between resistance of a thermistor and temperature

Answer 14

As temperature increases, resistance decreases

Question 15

What are thermistor’s used for?

Answer 15

thermostats

Question 16

equation for potential difference

Answer 16

V = IR
potential difference = current x resistance

Question 17

resistance of a wire RP: aim

Answer 17

investigate factors such as affecting the resistance of electrical circuits including the length of a wire at constant temperature and combinations of resistors in series and parallel

Question 18

resistance of a wire RP: variables

Answer 18

IV- length of wire
DV- current and potential differnce to calculate resistamce
CV- thickness and material of wire, temperature

Question 19

resistance of a wire RP: equation

Answer 19

V= IR

Question 20

resistance of a wire RP: equipment

Answer 20

battery, variable resistor, wires, voltmeter, ammeter, switch

Question 21

resistance of a wire RP: method
1. set up circuit with 10cm ___
2. set ___ to 2V
3. close the ___ and record ____ and ____ on the ammeter and voltmeter
4. ____
5. Calculate ___ for each length
6. plot a graph of ____ vs _______

Answer 21

1. wire
2. power supply
3. switch, current, potential difference
4. repeat
5. resistance
6. resistance, length of wire

Question 22

I-V characteristics RP: aim

Answer 22

investigate I-V characteristics of a variety of circuit elements

Question 23

I-V characteristics RP: Variables

Answer 23

IV- circuit component
DV- current and potential difference
CV- temperature

Question 24

I-V characteristics RP: equipment

Answer 24

battery, variable resistor, wires, voltmeter, ammeter, switch, as well as other components to test

Question 25

I-V characteristics RP: equation

Answer 25

V= IR

Question 26

I-V characteristics RP: method 1. set up circuit with component set to be tested - ____ 2. Set power supply to ____ 3. Close switch and record current and potential difference on ___ and ___ 4. repeat for a range of ____ by adjusting the ___ 5. ____ of the power supply and repeat 6. plot a graph of ____ vs ____ 7. repeat for ___ and ___

Answer 26

1. fixed resistor 2. 2V 3. ammeter, voltmeter 4. potential differences, variable resistor 5. reverse the direction 6. potential difference, current 7. bulb, diode

Question 27

ohms law:

Answer 27

the current through a resistor at constant temperature is directly proportional to the potential difference across it

Question 28

I-V characteristics for a fixed resistor:

Answer 28

directly proportional

Question 29

I-V characteristics for a filament bulb:

Answer 29

resistance increases as temperature increases (s shaped line)

Question 30

I-V characteristics for a diode

Answer 30

current only flows one direction, very high resistance in other direction (flat line with sudden peak)