# (c) Electromagnetism

## 6.11 know that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field

 The movement of the charged particle is a current so it produces a magnetic field. This magnetic field interacts with the permanent magnetic field to create a force. The force is perpendicular to the direction of motion and the permanent magnetic field.

## 6.12 understand why a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c. electric motors and loudspeakers

Motor

• Current flows in the wire/coil.
• This creates a magnetic field around the wire/coil.
• This magnetic field interacts with the field from the permanent magnet.
• This produces a force on the wire/coil which moves the wire/coil.
• The split-ring commutator changes the direction of the current every half turn as it spins. This reverses the direction of the forces, allowing the coil to continue spinning.

Loudspeaker

• An alternating current from the source passes though the coils in the speaker.
• This current is constantly changing direction and magnitude
• This current creates a magnetic field around the coil
• This field interacts with the magnetic field from the permanent magnets
• Creating a constantly changing force on the coil.
• This causes the coil to vibrate in and out as the direction of the force changes, moving the cone
• The cone causes vibrations which we hear as sound waves.

## 6.14 describe how the force on a current-carrying conductor in a magnetic field changes with the magnitude and direction of the field and current

 If you increase the magnitude of the current through a wire or the size of the magnet being used, you increase the force on the wire. If you change the direction of the current or reverse the poles of the magnet, you change the direction of the force on the wire
Select a set of flashcards to study:

Terminology

Skills and equipment

Remove Flashcards

Section 1: Principles of chemistry

a) States of matter

b) Atoms

c) Atomic structure

d) Relative formula masses and molar volumes of gases

e) Chemical formulae and chemical equations

f) Ionic compounds

g) Covalent substances

h) Metallic crystals

i) Electrolysis

Section 2: Chemistry of the elements

a) The Periodic Table

b) Group 1 elements: lithium, sodium and potassium

c) Group 7 elements: chlorine, bromine and iodine

d) Oxygen and oxides

e) Hydrogen and water

f) Reactivity series

g) Tests for ions and gases

Section 3: Organic chemistry

a) Introduction

b) Alkanes

c) Alkenes

d) Ethanol

Section 4: Physical chemistry

a) Acids, alkalis and salts

b) Energetics

c) Rates of reaction

d) Equilibria

Section 5: Chemistry in industry

a) Extraction and uses of metals

b) Crude oil

c) Synthetic polymers

d) The industrial manufacture of chemicals