5.1 - Current-Voltage Characteristics

Question 1

What is electric current?

Answer 1

The rate of flow of positive charge.

Question 2

What is current measured in?

Answer 2

Amperes (A) or amps

Question 3

What the equation to work out current?

Answer 3

I =ΔQ/Δt
I = current
ΔQ = change in charge
Δt = change in time

Question 4

What is charge?

Answer 4

A property of some particles that results in them being either attracted or repelled by other charged particles.

Question 5

What is charge measured in?

Answer 5

Coulombs (C).

Question 6

What is potential difference (voltage)?

Answer 6

The work done (energy converted) per unit charge moved.

Question 7

What is an ammeter?

Answer 7

A component of a circuit that measures the current flowing through a part of a circuit.

Question 8

What is the equation to find potential difference?

Answer 8

V = W/Q
V = voltage / potential difference (V)
W = work done (J)
Q = charge (C)

Question 9

What is a voltmeter?

Answer 9

A component of a circuit that measures the potential difference.

Question 10

What is the definition of a volt?

Answer 10

The potential difference across a component is 1 volt when you convert 1 joule of energy moving 1 coulomb of charge through the component. (1V = 1JC⁻¹)

Question 11

What is conventional current defined as?

Answer 11

The flow of positive charge from the positive terminal of a cell to the negative terminal. (conventional current always + –> -, electron flow opposite)

Question 12

How should ammeters always be connected to a circuit?

Answer 12

In series.

Question 13

How should voltmeters always be connected to a circuit?

Answer 13

In parallel.

Question 14

What is 1 volt equivalent to?

Answer 14

1 volt = 1JC⁻¹

Question 15

What is resistance?

Answer 15

The opposition to current.

Question 16

What is the relationship between p.d, resistance and current?

Answer 16

For a given p.d: the higher the resistance, the lower the current.

Question 17

What is the equation to find resistance?

Answer 17

R = V/I
R = resistance
V = p.d
I = current

Question 18

What is resistance measured in?

Answer 18

Ohms (Ω).

Question 19

What are ohms defined as?

Answer 19

One volt per ampere.

Question 20

What is Ohm’s law?

Answer 20

For a conductor at a constant temperature, the current through it is proportional to the potential difference across it.
(V=IR)

Question 21

What is the graph for plotting current against potential difference through a fixed resistor?

Answer 21

A straight line graph going through the origin.

Question 22

What is the graph for plotting current against potential difference through a fixed resistor?

Answer 22

A straight line graph.
(Gradient = 1/R)

Question 23

What is a component that obeys Ohm’s law?

Answer 23

A resistor.

Question 24

What is a material that doesn’t obey Ohm’s law?

Answer 24

A filament bulb.

Question 25

What do IV graphs show?

Answer 25

How current flowing through a component changes as the potential difference across it is increased.

Question 26

What do IV graphs of ohmic conductors look like?

Answer 26

Straight line graph. A steeper gradient means a low resistance (vice versa).

Question 27

What does the IV graph of a filament lamp look like?

Answer 27

An S shape curve (starts steep and gets shallower as the voltage rises).

Question 28

What does the IV graph of a semiconductor diode?

Answer 28

A horizontal line that goes sharply upwards at the end.

Question 29

How good are semiconductors at conducting electricity and why?

Answer 29

No where near as good as metals because there are far fewer charge carriers available.

Question 30

What are semiconductors useful for?

Answer 30

They are very good sensors for detecting changes in their environment.

Question 31

What are the 2 semiconductors that we look at in this specification?

Answer 31

Semiconductor diodes and thermistors.

Question 32

What is a semiconductor diode used for?

Answer 32

Used in a circuit to allow current to flow only in a specific direction. Forward bias - when current is in the direction of the arrowhead symbol. (Sharp increase in p.d) Reverse bias - switched around, does not conduct (0 p.d and I on the left side of the graph).

Question 33

Why does the IV graph of a filament lamp look like it does?

Answer 33

As current increases, temp increases. Filament is a metal, so increase in resistance. Resistance opposes the current, current increases at a slower rate.