P4- electric circuits 🪫💡

Question 1

What is a series circuit ?

Hint: branches

Answer 1

• a series circuit, is a circuit that has no branches, and the current can only flow in one path. [around the circuit]

Question 2

What is an electric current ?

Hint: a flow

Answer 2

• An electric current, is a flow of electric charge around a circuit

Question 3

How can we measure the current in a circuit ?

Answer 3

• we can measure the current in a circuit, using an ammeter.

Question 4

Fill in the gaps: In a series circuit, current is the ____ all the way around, and current is ______ ____ up in a circuit.

Answer 4

In a series circuit, current is the same all the way around, and current is never used up in a circuit.

Question 5

What is a conventional current ?

Hint: positive to negative

Hint #2: through

Answer 5

• A conventional current, is from the positive end, [through the conductor], to the negative end. [which is what scientists originally thought about current]

Question 6

What is a parallel circuit ?

Hint: split

Answer 6

• A parallel circuit, contains branches which means current is split.
• Some of the current passes through both of the branches and the current in the branches adds up to the total current, leaving the cell.

Question 7

What is potential difference [voltage] ?

Hint: 1 joule is transferred

Answer 7

• A potential difference of 1 volt, tells us that 1 joule of energy, is transferred for each coulomb of charge, that is moving through a circuit.

Question 8

What do we measure potential difference [voltage] with ?

Answer 8

• we measure potential difference with a voltmeter.

Question 9

In a series circuit, what can we say about the voltage?

Answer 9

Shared [and is equal to the total voltage across the cell]

Question 10

In a series circuit, what can we say about the current?

Answer 10

• In a series circuit, the current is the same everywhere

Question 11

In a parallel circuit, what can we say about the voltage?

Answer 11

• For components connected in parallel, the potential voltage across each component is the same.

Question 12

What is a battery ?

Hint: two or more, direction

Answer 12

• a battery, is two or more cells that are connected together
• ; the cells in a battery, must be connected in the same direction.

Question 13

How can you calculate the potential difference from batteries ?

Answer 13

• the potential difference of cells adds up, to give the total potential difference of the battery.

Question 14

What is electrical charge measured in ?

Answer 14

• electrical charge is measured in coulombs (C)

Question 15

• Fill in the gaps: The size of the ________ current, is the rate of ____ of electrical charge.

Answer 15

• The size of the electric current, is the rate of flow of electrical charge.

Question 16

• Fill in the gaps: The cell contains ________ energy, which is transferred to electrical energy, and then carried by the ________.
• But when the electrons pass through a component, the electrical energy is then __________ to other forms of energy.

Answer 16

• The cell contains chemical energy, which is transferred to electrical energy, and then carried by the current.
• But when the electrons pass through a component, the electrical energy is then transferred to other forms of energy.

Question 17

What can you tell me about resistance ?

Hint: drive a current

Answer 17

• resistance simply tells us the potential difference required, to drive a current through a component.

Question 18

What is an ohmic conductor ?

Hint: current

Answer 18

• in a ohmic conductor, current through a resistor is directly proportional to the potential difference.
• Therefore the resistance is constant and the resistance doesn’t change, if we increase the current.
• ; the resistance will only stay constant, if the temperature is constant.

Question 19

• Fill in the gaps: the current through a filament lamp, is not ________ ___________ to potential difference.
• This is because the filament gets hot, causing the __________ to increase.
• At high temperatures, the atoms in the filament _______ more and this means, the electrons in the current, now _______ more with atoms.
• Therefore, more energy is needed to push the _______ through the filament.

Answer 19

• the current through a filament lamp, is not directly proportional to potential difference.
• This is because the filament gets hot, causing the resistance to increase.
• At high temperatures, the atoms in the filament vibrate more and this means, the electrons in the current, now collide more with atoms.
• Therefore, more energy is needed to push the current through the filament.

Question 20

What is a key feature about a diode ?

Hint: why?

Answer 20

• the current through the diode, flows in one direction only.
• This is because, the diode has a very high resistance in the reverse direction.

Question 21

What are diodes useful for ?

Answer 21

• diodes are useful for controlling the flow of current in circuits, since no current can flow in the reverse direction

Question 22

What is a light- emitting diode [LED] ?

Hint: gives off

Answer 22

• an LED is a component that only allows current to flow in the forward direction; it gives off light when a current flows through.

Question 23

• Fill in the gaps: in a diode, the current increases in the ________ direction, as the _________ difference [voltage] increases

Answer 23

• in a diode, the current increases in the forwards direction, as the potential difference [voltage] increases

Question 24

Why are LEDs found in lots of appliances ?

Hint: light

Answer 24

• LEDs are extremely energy efficient sources of light, and this is why they are not only so useful, but found in lots of appliances.