S6 electricity - 1. current, potential difference and resistance

Question 1

what is current?

Answer 1

current is the rate of flow of charge

Question 2

which direction does conventional current flow?

Answer 2

conventional current flows from + to - of the cell (the opposite direction of electron flow)

Question 3

define one coulumb

Answer 3

one coulomb (C) is the amount of charge that passes in one second if the current is 1 ampere (A)

Question 4

what is an ammeter used for?

Answer 4

Ammeters are used to measure the current flowing through a component

Question 5

Potential difference is…

Answer 5

the energy per unit charge

Question 6

which direction do electrons flow?

Answer 6

Electrons flow from - to + of the cell (opposite to conventional current)

Question 7

what is a coulomb?

Answer 7

A coulomb is the unit of charge

Question 8

An ammeter always goes in…

Answer 8

SERIES to measure current flow.

Question 9

what is voltage?

Answer 9

Voltage is the energy per unit charge.

Question 10

A voltmeter always goes in…

Answer 10

parallel

Question 11

an ideal ammeter has…

Answer 11

no resistance at all. its 0

Question 12

an ideal voltmeter has…

Answer 12

infinite resistance

Question 13

why is it important that an ideal voltmeter has infinite resistance?

Answer 13

An infinite resistance ensures that no current is drawn, hence giving accurate readings of potential difference (V).

Question 14

why is it important to have an ideal ammeter?

Answer 14

resistance affects the measured amperage therefore if it’s 0 it wouldn’t affect the measured amperage.

Question 15

what is potential difference?

Answer 15

Potential difference is the energy per unit charge

Question 16

define potential difference

Answer 16

Potential difference (V) is defined as the work done per unit charge moved.

Question 17

what is a voltmeter used for?

Answer 17

A voltmeter is used to measure the potential difference across a component

Question 18

state the definition of the volt

Answer 18

The potential difference across a component is 1 volt when you convert 1 joule of energy moving 1 coulomb of charge through the component.

Question 19

state the equation for potential difference (V)

Answer 19

V =IR

V (voltage - potential difference)
I (current)
R (resistance)

Question 20

what is resistance measured in?

Answer 20

Resistance is measured in ohms (Ω)

Question 21

state ohms law

Answer 21

Provided the physical conditions, such as temperature, remain constant, the current through an ohmic conductor is directly proportional to the potential difference across it

Question 22

write the formula for current (not V=IR)

Answer 22

I = ΔQ / Δt

ΔQ is the charge in coulombs
Δt is the time taken in seconds

Question 23

what is potential difference measured in?

Answer 23

potential difference is measured in volts (V)

Question 24

what is current measured in?

Answer 24

Current is measured in amperes (A)

Question 25

define resistivity

Answer 25

Resistivity is a measure of the resisting power of a specified material to the flow of electric current.

Question 26

what is an ohmic conductor?

Answer 26

conductors that obey ohms law (mostly metals) are called ohmic conductors.

Question 27

state the formula for potential difference

Answer 27

V = W/Q