Science assessment task 1-2025

Electrostatic Force

• Types of Forces:

  • Contact Forces: Friction, air resistance, buoyancy, tension, normal force.

  • Non-Contact Forces (Field Forces): Electrostatic, magnetic, gravitational.

• Charging Objects:

  • Friction: Rubbing materials together can transfer electrons.

  • Induction: Bringing a charged object near a neutral object causes charge separation.

  • Conduction: Direct contact between a charged object and a neutral object transfers charge.

• Types of Charge:

  • Positive (protons) and negative (electrons).

  • Like charges repel, opposite charges attract.

• Atomic Model:

  • Nucleus containing protons (positive) and neutrons (neutral).

  • Electrons (negative) orbiting the nucleus.

• Electrostatic Force Definition:

  • A field force exerted between electrically charged objects.

• Electric Field Diagrams:

  • Vector diagrams showing the direction and strength of the electric field around charges.

  • Radial lines coming out of positive charges, and going into negative charges.

• Applications:

  • Lightning: Separation of charges in clouds leads to a large potential difference and discharge. Lightning rods provide a path for the discharge to the ground.

  • N95 masks: Electrostatic charge helps to trap small particles.

  • Spray painting: Electrostatic attraction between paint and object ensures even coating.

• Mathematical Representation:

  • Coulomb's Law: F=kr2q1q2 where F is force, k is Coulomb's constant, q1 and q2 are charges, and r is the distance.

2. Electric Circuits

• Circuit Components:

  • Batteries/power packs (voltage source).

  • Light bulbs (resistance/load).

  • Switches (control).

  • Resistors (control current).

  • Wires (conductors).

  • Voltmeters (measure voltage).

  • Ammeters (measure current).

• Open vs. Closed Circuits:

  • Open: Incomplete circuit, no current flow.

  • Closed: Complete circuit, current flow.

• Series vs. Parallel Circuits:

  • Series: Components connected in a single path.

  • Parallel: Components connected in multiple paths.

• Voltage (Potential Difference):

  • The electrical potential energy difference between two points.

  • Measured in volts (V).

• Current:

  • The flow of electric charge.

  • Measured in amperes (A).

• Relationship between Voltage, Current, and Brightness:

  • Increasing voltage increases current and brightness of a light bulb.

• Resistance:

  • Opposition to the flow of current.

  • Measured in ohms (Ω).

• Conductors and Insulators:

  • Conductors: Materials with low resistance (e.g., metals).

  • Insulators: Materials with high resistance (e.g., rubber, glass).

• Energy Transformations:

  • Electrical energy to light and heat in a light bulb.

  • Electrical energy to mechanical energy in a motor.

• Law of Conservation:

  • Energy cannot be created or destroyed but only transferred/transformed.

• Analogy:

  • Voltage as water pressure, current as water flow, resistance as pipe diameter.

• Ohm's Law:

  • V=IR where V is voltage, I is current, and R is resistance.

3. Magnetism

• Magnetic Poles:

  • North and south poles.

  • Like poles repel, opposite poles attract.

• Magnetic vs. Non-Magnetic Materials:

  • Magnetic: Iron, nickel, cobalt.

  • Non-magnetic: Wood, plastic, aluminum.

• Magnetic Fields:

  • Regions around magnets where magnetic forces are exerted.

  • Field lines show the direction and strength of the field.

• Compass:

  • A magnetic needle that aligns with the Earth's magnetic field.

• Electromagnets:

  • Magnets created by passing an electric current through a coil of wire.

  • Advantages: Strength can be controlled, can be turned on/off.

  • Applications: Metal separation, doorbells, electronic locks.

• Relationship between electricity and magnetism:

  • A current creates a magnetic field.

  • A changing magnetic field creates a current.

Key Connections

• Electromagnetism: The interplay between electricity and magnetism.

• Electric circuits rely on the movement of charged particles (electrons), which are affected by electrostatic forces.

• Electromagnets demonstrate the link between electric current and magnetic fields.

sIMPLE VERSION:

• Energy is the ability to do work.

• Work is done when a force on an object causes it to move or change shape.

Units:

• Energy is measured in joules (J).

Types of energy

• Kinetic energy: energy possessed by moving objects

• Potential energy: stored energy

• Electromagnetic energy: energy carried by electromagnetic waves eg. Light, UV

Energy is not a substance – it is not made of matter, so it has no mass. So we can’t see energy (apart from light), but we can see its effect on objects.

Physics: Electricity and Magnetism Notes

Electrostatic Forces

Objects and Charging

Objects can become electrostatically charged through:

• Friction (rubbing materials together)

• Contact (touching charged objects)

• Induction (bringing charged object near another without contact)

Types of Charge

• Positive charge (protons)

• Negative charge (electrons)

Like charges repel, opposite charges attract

Atomic Model

Components and their locations:

• Protons (positive) - in nucleus

• Neutrons (neutral) - in nucleus

• Electrons (negative) - orbiting nucleus in shells

Electric Fields

Electric field is the region around a charge where it exerts a force on other charges.

<aside> Field lines point away from positive charges and toward negative charges

</aside>

Applications

Lightning and Protection:

• Lightning occurs due to charge buildup in clouds

• Lightning rods provide safe path for charges to ground

Electric Circuits

Circuit Components and Symbols

Circuit Types

Series Circuits:

• Components connected end-to-end

• Same current throughout

Parallel Circuits:

• Components connected across each other

• Same voltage across branches

Electrical Quantities

Magnetism

Magnetic Properties

When magnetic poles interact:

• Like poles repel

• Unlike poles attract

Magnetic Materials

Examples of magnetic materials:

• Iron

• Nickel

• Cobalt

Magnetic Fields

Properties:

• Field lines go from North to South pole

• Stronger field shown by closer field lines

Electromagnets

Advantages over permanent magnets:

• Can be turned on/off

• Strength can be varied

• Polarity can be reversed

Applications:

• Scrap metal sorting

• Electric doorbells

• Security systems

• Electric motors

Electrostatic Forces

Objects and Charging

Objects can become electrostatically charged through:

• Friction (rubbing materials together)

• Contact (touching charged objects)

• Induction (bringing charged object near another without contact)

Types of Charge

• Positive charge (protons)

• Negative charge (electrons)

Like charges repel, opposite charges attract

Atomic Model

Components and their locations:

• Protons (positive) - in nucleus

• Neutrons (neutral) - in nucleus

• Electrons (negative) - orbiting nucleus in shells

Electric Fields

Electric field is the region around a charge where it exerts a force on other charges.

<aside> Field lines point away from positive charges and toward negative charges

</aside>

Applications

Lightning and Protection:

• Lightning occurs due to charge buildup in clouds

• Lightning rods provide safe path for charges to ground

Electric Circuits

Circuit Components and Symbols

Circuit Types

Series Circuits:

• Components connected end-to-end

• Same current throughout

Parallel Circuits:

• Components connected across each other

• Same voltage across branches

Electrical Quantities

Magnetism

Magnetic Properties

When magnetic poles interact:

• Like poles repel

• Unlike poles attract

Magnetic Materials

Examples of magnetic materials:

• Iron

• Nickel

• Cobalt

Magnetic Fields

Properties:

• Field lines go from North to South pole

• Stronger field shown by closer field lines

Electromagnets

Advantages over permanent magnets:

• Can be turned on/off

• Strength can be varied

• Polarity can be reversed

Applications:

• Scrap metal sorting

• Electric doorbells

• Security systems

• Electric motors