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Charge, Electric Current and Power

In this worksheet, students explore what charge is and how it provides electric current and power.

Key stage:  KS 4

Curriculum topic:  Physics: Electricity

Curriculum subtopic:  Exploring Current, Resistance and Voltage Relationships

Difficulty level:  

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QUESTION 1 of 10

An electric current is a flow of electric charge, carried by negatively charged electrons in atoms of metals. Electrons are free to move and flow in a direction opposite to the conventional current. Cells and batteries supply direct current (DC), which flows only in one direction. Generators produce alternating current (AC), in which the electrons change direction many times in a second. The current in a circuit is measured in amperes (A) using an ammeter, which must be connected in series to the circuit. The potential difference (pd) between two points in a circuit is the difference in voltage. This is measured in volts (V) using a voltmeter. A voltmeter is always connected in parallel.


A defibrillator delivers a controlled electric shock through a patient's chest to restart their heart. Two paddles are charged form a high voltage supply. They are placed firmly on the patient's chest to ensure good electrical contact. Electric charge is passed through the patient to make their heart contract. Once the heart is restarted, it is hoped it will continue normally. A typical shock from a defibrillator supplies around 400 J of energy in a few milliseconds (1 millisecond = 0.001 seconds). If we assume that a defibrillator is switched on for 5 milliseconds, we can calculate the power like this:


 

We will now answer some questions on electrical charge and power.

What is an electric current?

a flow of protons

a flow of neutrons

a flow of charge

What provides charge in an electric current?

electrons

protons

neutrons

What is the unit of electric current?

ammeters

amperes

volts

What is the instrument used to measure electric current?

defibrillator

ammeter

voltmeter

How is an ammeter connected in a circuit? In series or parallel?

in series

in parallel

What is another word for potential difference?

 

wattage

charge

voltage

How is a voltmeter connected in a circuit?

in series

in parallel

What is a defibrillator?

a piece of ultrasound equipment

a screening apparatus used in hospitals

an instrument that delivers electric charge to a patient's chest to restart their heart

How much energy does a typical shock from a defibrillator pass to the heart in one millisecond?

300J

400J

500J

What do you need to divide energy by to calculate power?

time

speed

distance

  • Question 1

What is an electric current?

CORRECT ANSWER
a flow of charge
EDDIE SAYS
An electric current is a flow of electric charge.
  • Question 2

What provides charge in an electric current?

CORRECT ANSWER
electrons
EDDIE SAYS
Electric current is carried by negatively charged electrons in atoms of metal.
  • Question 3

What is the unit of electric current?

CORRECT ANSWER
amperes
EDDIE SAYS
The unit of electric current is ampere.
  • Question 4

What is the instrument used to measure electric current?

CORRECT ANSWER
ammeter
EDDIE SAYS
The instrument used to measure electric current is an ammeter.
  • Question 5

How is an ammeter connected in a circuit? In series or parallel?

CORRECT ANSWER
in series
EDDIE SAYS
An ammeter is connected in a circuit in series.
  • Question 6

What is another word for potential difference?

 

CORRECT ANSWER
voltage
EDDIE SAYS
Another word for potential difference is voltage, and it means the difference between two points in a circuit.
  • Question 7

How is a voltmeter connected in a circuit?

CORRECT ANSWER
in parallel
EDDIE SAYS
A voltmeter is always connected in a circuit in parallel.
  • Question 8

What is a defibrillator?

CORRECT ANSWER
an instrument that delivers electric charge to a patient's chest to restart their heart
EDDIE SAYS
A defibrillator delivers electric charge to a patient’s chest to get their heart restarted.
  • Question 9

How much energy does a typical shock from a defibrillator pass to the heart in one millisecond?

CORRECT ANSWER
400J
EDDIE SAYS
A typical shock from a defibrillator passes to the heart 400J in one millisecond.
  • Question 10

What do you need to divide energy by to calculate power?

CORRECT ANSWER
time
EDDIE SAYS
You need to divide energy by time to calculate power.
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