Electricity and Circuits

• Science
• Further Education (Key Stage 5)

Electricity

Switch

Cell

Battery

Motor

Voltmeter

Ammeter

Resistor

Variable Resistor

Bulb

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Electrical Charge

Some particles carry an electric charge.

In electric wires these particles are electrons.

Electrons are negatively charges.

We get an electric current when these charged particles move from place to place.

Charge

• Electrons are negatively charged particles
• They transfer energy through wires as electricity
• Charge is measured in coulombs (C)

Charge

• Since electrons are very small
  
• One electron will not have much of an effect
  
• It is more useful to refer to packages of electrons
  
• One coulomb of charge is a package equivalent to 6,250,000,000,000,000,000 electrons
  

How many electrons are in one coulomb of charge?

1. 10,000,000,000
2. 6,250,000,000,000,000,000
3. 100,000,000,000,000
4. 1,000,000

How is charge measured?

1. In amperes (A)
2. In coulombs (C)
3. In volts (V)
4. In ohms (Ω)

What is the charge of electrons?

1. Partially charged
2. Negatively charged
3. Neutral
4. Positively charged

Electrical Current

• We need two things for an electric current to flow:
  
• Something to transfer energy to the electrons, such as a battery or power pack
  
• A complete path for the electrons to flow through (an electric circuit)
  

Current

• Current is a measure of how much electric charge flows through a circuit
• Current flows from positive to negative
• The more charge that flows, the bigger the current.
• Measured in Amperes (A) or amps
• Symbol = I

Measuring current

• An ammeter is used to measure current
  
• Ammeter can have a pointer on a dial, or a digital display.
  
• To measure the current flowing through a component in a circuit, you must connect the ammeter in series with it.
  

Current Equation

When current flows, electrical work is done and energy transferred.

The amount of charge passing a point in the circuit can be calculated using the equation:

charge = current × time

𝑸=𝑰 𝒙 𝒕

Charge (Q) in coulombs (C)

Current (I) in amps (A)

Time (t) in seconds (s)

What is the equation to calculate the amount of charge passing a point in a circuit?

1. Q = I x t
2. Q = t / I
3. Q = I / t
4. Q = I + t

How is an ammeter connected to measure current?

1. In parallel
2. Across the component
3. In series-parallel
4. In series

What is an ammeter used to measure?

1. Power
2. Current
3. Resistance
4. Voltage

How is current calculated using the current equation?

1. charge = current × time
2. charge = current ÷ time
3. charge = current + time

In which direction does current flow?

1. From positive to negative
2. From negative to positive
3. In both directions

What is the unit for measuring current?

1. Volts (V)
2. amps
3. Amperes (A)
4. Joules (J)