Topic 10 - Electricity And Circuits

Question 1

In a closed circuit, if theres potenial difference in the circuit there will be a

Answer 1

Current

Question 2

What is current?

Answer 2

The rate of flow of charge (or electrons) around a circuit

Question 3

Unit for charge

Answer 3

Coulombs, C

Question 4

Draw a switch circuit symbol

Answer 4

Closed the line goes across

Question 5

Draw the circuit symbol for a cell

Answer 5

Question 6

Draw circuit symbol for battery

Answer 6

Question 7

Draw circuit symbol for a lamp

Answer 7

Question 8

Draw the circuit symbol for a fuse

Answer 8

Question 9

Draw the circuit symbol for a voltmeter

Answer 9

Question 10

Draw the circuit symbol for an ammeter

Answer 10

Question 11

Draw the circuit symbol for a diode

Answer 11

Question 12

Draw the circuit symbol for a resistor

Answer 12

Question 13

Draw the circuit symbol for a thermistor

Answer 13

Question 14

Draw the circuit symbol for a variable resistor

Answer 14

Question 15

Draw the circuit symbol for an LDR

Answer 15

Question 16

Draw the cicuit symbol for an LED:

Answer 16

Question 17

Ways a component can be connected in a circuit?

Answer 17

Series (same loop)

Parallel (adjacent loop)

Question 18

Voltage is know as

Answer 18

Potenial difference

Question 19

How does p.d across two components vary when connected in series and parallel?

Answer 19

In series, total P.D is shared between each component

In parallel circuit the P.D across each component is the same

Question 20

2 resistors are connected in parallel, what can be said about their combined total resistance?

Answer 20

Their total resistance is less than smallest of the two indivual resistances

Question 21

2 resistors are connected in series, what can be said about their total resistance?

Answer 21

Total combined resistance is equal to the sum of the two individual resistances.

Question 22

Where must a voltmeter be placed in a circuit?

Answer 22

In parallel with the component that is being measured

Question 23

Give an equation relating potenial difference with energy transferred and charge.

Answer 23

Potenial difference = energy transferred/ charge

V=E/Q

Question 24

A volt can be described as..

Answer 24

Joule per coulomb

Question 25

What is an electric current?

Answer 25

The rate of flow of charge

Question 26

Give the equation linking charge, current and time

Answer 26

``` Q = I x t Charge = current x time Coulombs = current x time ```

Question 27

What can be said about the value of current at any point in a single closed loop?

Answer 27

Current is the same at all points in a closed loop.

Question 28

Factors that current in a circuit depends on?

Answer 28

``` Potential difference (V) Resistance (R) ```

Question 29

Equation for P.D (current and resistance are known)

Answer 29

V = I x R | Potenial difference = resistance (ohms/A) x current (I)

Question 30

What is an ammeter and where must it be connected in a circuit?

Answer 30

An ammeter measure current. It is placed in series with the component it is require to measured.

Question 31

What happens when current reaches a junction in a circuit?

Answer 31

Current is conserved; the total current remains the same is split between the two branches.

Question 32

How does resistance affect current in a circuit?

Answer 32

As total resistance of a circuit increases, the current flowing through the circuit decreases.

Question 33

How can the current in a circuit be varied?

Answer 33

Using a variable resistor

Question 34

Equation linking current and resistance

Answer 34

Current (A) x Resistance (ohms) = p.d (V) | V = IR

Question 35

How is total resistance affected by two resistors in series?

Answer 35

The total resistance increases; equal to the sum of the two resistors

Question 36

How is total resistance affected by two resistors in parallel?

Answer 36

The total resistance decreases; it is less than the resistance of the resistor with the lowest resistance.

Question 37

What is an “Ohmic Conductor”? State the condition required

Answer 37

A conductor for which current and p.d are directly proportional Resistance remains constant as current changes Temperature must be constant

Question 38

List four components for which resistance is not constant as current changes

Answer 38

Filament lamps Diodes Thermistors Light dependent resistors (Ldrs)

Question 39

What happens to the resistance of a filament lamp as the temperature increases? Why?

Answer 39

Resistance increases Metal ions have more KE, so vibrate more, colliding more frequently with electrons as they flow through the metal This creates more resistance to current.

Question 40

What is different about current flow through a diode?

Answer 40

The current only flows in one direction. | Resistance is very high in the other direction, preventing current flow.

Question 41

State what happens to the resistance of a thermistor as temperature increases

Answer 41

The thermistor resistance decreases

Question 42

Give two examples of when a thermistor may be used

Answer 42

In a thermostat to turn a heater on below a certain temperature In a freezer to turn on cooler when temperature is too high

Question 43

State what happens to the resistance of an LDR as light intensity decreases

Answer 43

The LDR’s resistance increases

Question 44

Give an application for a LDR

Answer 44

Street lamps or night lights

Question 45

How do diodes work?

Answer 45

A diode only allows current to flow in one direction. If current is flowing the right way, the resistance is large for small voltages (up until 0,6V) then becomes very small at higher voltages

Question 46

What electrical component does this graph represent?

Answer 46

Diode

Question 47

What factors affect the enery transferred when charge flows through a component?

Answer 47

Amount of charge | The potenial difference across the component

Question 48

Equation linking energy, current and p.d and time

Answer 48

Energy (J) = p.d (V) x current (A) x time (s) | E = v x I x t

Question 49

Define p.d in terms of charge

Answer 49

The work done per unit charge

Question 50

Equation relating p.d to charge

Answer 50

``` Energy transferred (J) = Charge (C) x p.d (V) E=QV ```

Question 51

When an electrical current flows through a resistor, why does it heat up?

Answer 51

There are collisions between electrons and the ions in the resistors lattice. This causes a transfer of KE into thermal energy which is released into the surroudings.

Question 52

How do low resistance wires reduce unwanted energy transfers?

Answer 52

A smaller resistance will mean there are fewer collisions, therefore less energy will be wasted through heating.

Question 53

What are some advantages of the heating effect?

Answer 53

It is useful for appliances such as toaster or electricity fires, where the heat is the desired product.

Question 54

What are some disadvantages of the heating effect?

Answer 54

The loss of energy as heat energy can make an appliance inefficient If an appliance overheats it can catch fire or overheat, which could ruin the device or injure the user.

Question 55

Energy transferred per second is also known as..

Answer 55

Power

Question 56

What is power?

Answer 56

The rate of energy transfer, or the rate at which work is done.

Question 57

Units for power

Answer 57

Watts, W

Question 58

Equation linking power and p.d

Answer 58

Power (W) = current (A) x p.d (V).

Question 59

Equation for power without p.d

Answer 59

Power (W) = current^2 (A) x resistance (ohms) | P = I^2R

Question 60

Equation linking power and energy

Answer 60

Power (W) = energy (J) / Time(s)

Question 61

Both equations linking power with resistance

Answer 61

``` P = I^2 x R P = V^2 / R ```