Non contact forces and electricity

Electric current

Electric current

• How fast electrons flow through a circuit (speed)

• Electrons flow along a wire from the negative terminal of the battery to the positive terminal.

• The higher the current, the more energy (electrons) is supplied. For example, increasing the current makes a light bulb glow brighter.

Ampere

• The unit of measurement for electric current

• Amperes or amps have the symbol A.

Circuit

A pathway for electricity to flow through

A circuit must contain an unbroken path that electrons can flow through.

Voltage

• The amount of energy given to electrons

• Increasing the voltage in a circuit gives electrons more energy.

• This makes them move faster, increasing the current.

• Voltage is measured in volts (V)

Resistance

• A material’s opposition to the flow of electric current. 

• Measured in Ohms (Ω)

Ohm’s Law

The relationship between current, voltage and resistance

Voltage (V) = Current (I) x Resistance (R)

Current (I) = Voltage (V) ➗ Resistance (R)

Resistance (R) = Voltage (V) ➗ Current (I)

Series circuits

• Series circuits have a single path for electrons to flow through. 

• As you connect more bulbs in the circuit, the current flow decreases so the bulbs do not glow as bright

Parallel circuits

• There is more than one pathway electrons can take

• Only part of the current flows through any branch 

• As you add more bulbs to the circuit, it does not affect the current flow. So the bulbs do not decrease in brightness 

Parallel vs series circuits

 

Parallel Circuits	Series Circuits
Each branch of the circuit has the same voltage	Voltage split evenly between identical components
Current split for the branches	Current is the same through all components
One component blows, only that branch affected	One component blows, whole circuit breaks
Components can be controlled individually	Components cannot be controlled individually

Magnetic force

• Magnets can only push (repel) and pull (attract) on magnetic objects.

• Non contact force

magnets vs electrostatic forces

magnets consist of poles, electrostatic forces consist of charges

Electrostatic force

• The force produced when charged objects push/ pull on other objects.

• The electrostatic force between two objects is greater:

  • When they are more charged or,

  • When they are closer to one another.

• When an object gains electrons it becomes more negatively charged and when it loses electrons it becomes more positively charged.

• Unlike charges attract

• Like charges repel

• Non contact force

Gravitational force

• Force of attraction between 2 objects with mass

• Non-contact force

Magnets

• Magnets attract certain metals only, which are said to be magnetic

• Only magnetic items can be magnetised (made into magnets)

• Like poles repel, unlike poles attract 

• two north +south poles will repel each other (same charge)

• one north pole will attract one south pole (opposite charge)

How magnetic force works

• It is always strongest near a magnet, and becomes weaker as you get further from it

• The ends (poles) of magnets are more magnetic than the middle

Magnetic fields

• The interaction between poles which create a magnetic field, an invisible area around the magnet where magnetic forces are exerted.

• When you bring two magnets together, you can feel the force of attraction or repulsion between them 

• The magnets exert a non-contact force on each other (they don’t touch)

• When something magnetic is in this field, it will experience a force

• The closer to the magnet, the stronger the magnetic field

Static Electricity

• The build-up of electrical charge on a surface.

• Often generated when two surfaces are rubbed together

• Electrons from one object are passed to another

Current Electricity

• The electricity from a battery or a power point is made up of electrons moving along a wire.

• Moving electrons have energy that is transferred into another form of energy.

• When electrons pass through globes or motors their energy changes into other forms of energy.

Conductor

A material that electricity moves through easily

• Iron

Insulators

A material that resists the flow of electric current or heat

• Plastic

Non contact force

A type of force that acts on an object without any physical contact between the objects involved.

Electromagnets

• the relationship between magnets and electric current

• When an electric current flows through a wire, a magnetic field forms around it

• To make an electromagnet, a wire is wrapped around an iron rod.

• When current is passed through, a stronger magnetic field is produced.

Electric circuits