2. Circuits

Question 1

Definition of current

Answer 1

The rate of flow of charge

Question 2

Current Units

Answer 2

Amps

Question 3

Current equation

Answer 3

I = Q / T

Question 4

Unit for charge

Answer 4

Coulombs

Question 5

What equation do you use to figure out the speed of electrons in a conductor?

Answer 5

I = naVe

Question 6

What does drift velocity mean

Answer 6

How fast each electron moves

Question 7

What does the n stand for in I= naVe

Answer 7

Charge carrier density = number of electrons per meter

Question 8

How to derive I = naVe

Answer 8

time = length / velocity
N = volume x charge carrier density
Charge of an electron = e

Question 9

Definition of potential difference

Answer 9

The energy supplied per unit charge

Question 10

Unit of Pd

Answer 10

Volts

Question 11

Equation to find voltage

Answer 11

V = IR or V = E / Q

Question 12

Definition of resistance

Answer 12

The ratio of potential difference to current

Question 13

Equation for resistance

Answer 13

R = V /I

Question 14

How does resistance occur

Answer 14

The collisions between free electrons and the ions means it is harder for electrons to flow

Question 15

What happens when temp is increased within a conductor

Answer 15

Resistance increases as it is proportional to temperature
The kinetic energy of particles increases so particles are moving faster so they collide more therefore higher resistance and temp

Question 16

What is ohms law

Answer 16

R is constant for all values of V and I

Question 17

What is the equation for resisitivity

Answer 17

Resistance = (Resistivity x length) / area

Question 18

What is resistivity

Answer 18

The general measurement of how much a material resists the flow of current
It stays constant for the same type of material

Question 19

What is the unit for resistivity

Answer 19

Ohm - metre

Question 20

What is the IV graph for a filament lamp

Answer 20

Curved starting from the origin

Question 21

What is the IV graph for a metal wire at a constant temp

Answer 21

Directly proportional

Question 22

What is power

Answer 22

The amount of energy transferred per unit of time

Question 23

Power equation

Answer 23

P = IV or P = E/ T

Question 24

What is superconductivity

Answer 24

When a material conducts with zero resistance

Question 25

What is the transitional temperature

Answer 25

The temperature which a super conductor needs to be cooled down to

Question 26

How are superconductors used

Answer 26

Used to create magnets used in trains MRI scanners Particle accelerators

Question 27

What quantities are equal across branches in a parallel circuit

Answer 27

Potential difference

Question 28

What happens to current in a parallel circuit

Answer 28

Each branch must add up to the current through the source

Question 29

What is the difference between sum of resistance in a series circuit and in a parallel circuit

Answer 29

Series= resistors all add up Parallel= Reciprocal of the sum of reciprocals

Question 30

What is a potential divider

Answer 30

When there are two resistors in series

Question 31

What is a potential divider used for

Answer 31

To supply a variable voltage to an external circuit

Question 32

What is a thermistor

Answer 32

A temperature sensitive device that reduces resistance when heated

Question 33

What is an LDR

Answer 33

Light dependent resistor Made out semi conductor material they have a lower resistance when exposed to the lighyt

Question 34

What happens when light intensity increases on a circuit with a LDR

Answer 34

The resistance of the LDR decreases so the potential difference also decreases

Question 35

What is EMF

Answer 35

Electromotive force

Question 36

Definition of emf

Answer 36

The energy supplied per unit charge from the source

Question 37

What is the equation with EMF

Answer 37

V = E - Ir

Question 38

What do you do when a series circuit has multiple cells

Answer 38

Add up all the emf and add up the internal resistance to make overall total of one cell

Question 39

What is a diode

Answer 39

A component that only allows current to flow in one direction

Question 40

What is Kirchoffs first law

Answer 40

All of the current going to a junction is equal to the total current leaving the junction

Question 41

What is Kirchoffs second law

Answer 41

The sum of potential differences must equal the total emf of the circuit