P3 - Circuits - The Basics

Question 1

What type of circuit is required for current to flow?

Answer 1

A closed circuit

Question 2

What is the unit of current?

Answer 2

Ampere (A)

Question 3

What is the unit of potential difference (or voltage)?

Answer 3

Volt (V)

Question 4

What is the unit of resistance?

Answer 4

Ohm

Question 5

Resistance, current and potential difference are all related, what formula illustrates this?

Answer 5

V=IR
Potential difference (V) =Current (I) x Resistance (R)

                V
          ———-
             I x R

Question 6

If the potential difference of a circuit is increased whilst the resistance remains the same, what will happen to the current?

Answer 6

The current will increase.

Question 7

If the resistance of the circuit is increased whilst the potential difference remains the same, what will happen to the current?

Answer 7

The current will decrease

Question 8

What happens to charges as they flow the continuous loop of a circuit?

Answer 8

They are not used up, but transfer energy to components as they do work

Question 9

What formula do you use to calculate the total charge?

Answer 9

Charge (coulombs C) = Current (A) x Time (s)

            Q
   —————
          I x t

Question 10

A laptop charger passes a Current of 8.0A through a laptop battery. Calculate how long the charger needs to be connected to the battery for 28 800C of charge to be transferred to the laptop?

Answer 10

Q 28,800
——- = ————
I x t 8.0 x ?
= 28,800 / 8.0 = 3,600 s or 3,600 x 60 = 60 mins (1 hour)