P4 - Electric Circits

Question 1

What is an electric current?

Answer 1

• An electric current is a flow of charge.
• Most electric currents use a flow of electrons (negatively charged).
• Current is measured in amps (A).

Question 2

What is a circit diagram?

Answer 2

• A circuit diagram shows how the components in an electrical circuit are connected.
• Each component has its own symbol.
• When drawing a circit diagram use straight, clear lines.

Question 3

What do cells and batteries do in an electrical circit? (Components)

Answer 3

Provide the ‘push’ for electrons in a circit.

Question 4

What does an ammeter do in an electrical circit? (Component)

Answer 4

Used to measure current.

Question 5

What does a voltmeter do in an electrical circit? (Component)

Answer 5

Used to measure the potencial difference (voltage).

Question 6

What does a lamp do in an electrical circit? (Component)

Answer 6

Ouputs light when current flows through it.

Question 7

What does a resistor do in an electrical circit? (Component)

Answer 7

Limits the current in a circit

Question 8

What is an LDR? (Component)

Answer 8

Light dependent resistor

Question 9

What does a fuse do in an electrical circit? (Component)

Answer 9

Melts and breaks the circit if the current is too high.

Question 10

What does an LED do in an electrical circit? (Component)

Answer 10

Emitts light when current passes through it

Question 11

What does a switch do in an electrical circit? (Component)

Answer 11

Enables current in a circit to be switched on or off.

Question 12

What does a thermsistor do in an electrical circit? (Component)

Answer 12

Temperature dependent resistor.

Question 13

What does a variable resistor do in an electrical circit? (Component)

Answer 13

Allows current to be varied.

Question 14

What is the unit for charge

Answer 14

Coulombs (C)

Question 15

What is the charge of an electron

Answer 15

-1 atomic charge

or

-1.6x10^-19 Coulombs

Question 16

What does a motor do in an electrical circit? (Component)

Answer 16

Turns electrical energy into kinetic energy

Question 17

What does a diode do in an electrical circit? (Component)

Answer 17

Diodes only let electricity go one direction in the circit

Question 18

Write an equation that connects charge, current and time.

Answer 18

Q = I x t

Q is Charge (Coulombs)
I is Current (Amps)
t is time (seconds)

Question 19

Conventional current flows from _________ to _______.

Answer 19

positive, negative

Question 20

Electron flow is from the _______ terminal of the cell to the _______ terminal of the cell.

Answer 20

negative, positive

Question 21

Electron flow is _________ to convencional current direction.

Answer 21

opposite

DO NOT GET MIXED UP

Question 22

What is potential difference (also known as voltage)?

Answer 22

Potential difference is the amount of work done (energy transferred) by each coulomb of charge that passes through the circuit between two points.

Question 23

Write an equation connecting potential difference, charge and energy.

Answer 23

Potential difference (V) = Energy (J) / Charge (C)

V = E/Q

Question 24

What are some different equations for electrical energy?

Answer 24

Energy(J) = Power(W) x time(s)

Energy(J) = Charge(C) x Potential difference(V)

Energy(J) = Current(A) x time(s) x Potential difference(V)

Question 25

Name a metal that is a better conductor than copper.

Answer 25

Gold is a better conductor than copper. But due to how expensive it is, its mostly used in smaller appliances like inside a phone.

Question 26

How does current and voltage behave in a series circuit?

Answer 26

- The current stays the same throughout the circuit - The voltage is split across each component (e.g bulbs)

Question 27

How does current and voltage behave in a parallel circuit?

Answer 27

- The current is split between each of the components (e.g bulbs) - The voltage stays the same throughout the circut

Question 28

What is resistance?

Answer 28

- Electrical resistance in a circuit is the opposition to the flow of charge - Resistance is measured in a unit called Ohms (Ω)

Question 29

How does resistance work?

Answer 29

- Electricity is the flow of electrons along a wire. As the electrons move along the wire they collide with the metal ions in the wire. - These collisions are what causes resistance

Question 30

What happens in metals with a high resistance when they conduct electricity?

Answer 30

- In metals with a high resistance, more collisions occur and electrical energy is wasted as light and heat. - The current decreases and the metal gets hotter.

Question 31

How do filament bulbs turn electrical energy into light?

Answer 31

- Filament bulbs use a thin wire with a high resistance. - This causes the electrons to collide more with the metal atoms. - This turns the electrical energy into heat and light energy.

Question 32

Electrical energy will always flow in the path with the ___________.

Answer 32

least resistance

Question 33

What is a resistor?

Answer 33

A resistor is a component designed to reduce the current. - A variable resistor has a resistance that can be changed. - A fixed resistor has a resistance that remains the same.

Question 34

How do kettles transfer electrical energy into heat energy to boil water?

Answer 34

The heating element in this kettle is a coil of metal that resists electricity. - As current is passed through the metal, resistance causes the metal to get hot and so boils the water.

Question 35

What factors affect the resistance of the wire

Answer 35

- How thin it is - thinner wires increase resistance. - How hot it is - a hotter wire increases resistance. - the length of the wire - longer wires have a higher resistance. - The material used - the reactivity of a material is always the same.

Question 36

What is Ohm's law?

Answer 36

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

Question 37

Write Ohm's law as an equation.

Answer 37

Potential difference(V) = Current(A) x Resistance(Ω) V=IxR

Question 38

In a _______ circuit the total resistance in the circuit is the the resistance of the all the resistors added up.

Answer 38

series

Question 39

Categoric data is usually displayed using a...

Answer 39

... bar chart.

Question 40

Continuous data is usually displayed using a...

Answer 40

... line graph

Question 41

A current-voltage graph the line of best fit will always pass through the...

Answer 41

origin (0,0). (As long as the temperature remains constant while collecting data)

Question 42

The gradient of a current-voltage graph is equal to...

Answer 42

... 1/resistance.

Question 43

In a current-voltage graph a line of best fit with a steeper gradient means that the material has a ______ resistance.

Answer 43

lower

Question 44

Why does a filament lamp not follow Ohm's law?

Answer 44

Its resistance increases as the temperature of its filament increases. So the current flowing through a filament lamp is not directly proportional to the voltage across it.

Question 45

The diode has a very high resistance in ____________. This means that current can only flow in the ____________.

Answer 45

one direction other direction

Question 46

What are diodes used for and why?

Answer 46

Diodes are electronic components that can be used to regulate the voltage in circuits and to make logic gates. Light-emitting diodes (LEDs) give off light and are often used for indicator lights in electrical equipment such as computers and television sets.

Question 47

Memorise the voltage current graphs for the following components...

Answer 47

Resistor Filament lamp Diode

Question 48

How is the total resistance of a circuit calculated in a series circuit?

Answer 48

RT = R1 + R2 + R3 Adding components in series increases the total resistance in a circuit.

Question 49

How is the total resistance of a circuit calculated in a parallel circuit?

Answer 49

1/RT = 1/R1 + 1/R2 + 1/R3