Electric Charge and Electromagnetism

Key Issues

Titles

Chapters

• A charged body can be discharged by connecting it to earth with a conductor. Charge then flows through the conductor
• Changing the Size of a Force
• Charges on Isolated Bodies
• Charging by friction (rubbing)
• Common electrostatic phenomena
• Common electrostatic phenomena (sparks, lightning)
• Conductors
• Conductors and Forces
• Current
• Dangers and uses of electrostatic charges
• describe the dangers and use of electrostatic charge generated in everyday contexts
• Direction of Force
• Earthing removes excess charge (electrons) on a body
• Electric Charge
• Electrical charges can move easily through some substances, eg metals
• Electrical Potential Difference
• Electrostatic charges can be useful, for example in photocopiers and smoke precipitators and the basic operation of these devices
• Exertion of Forces
• Force on a current-carrying wire in a magnetic field - the motor effect
• Force perpendicular to both the current-carrying wire and the magnetic field
• Forces between like and unlike charges
• If the potential difference becomes high enough a spark may jump across the gap between the body and any earthed conductor which is brought near it
• Like and unlike charges
• Metals and Electrical Charges
• Negatively charged electrons are rubbed off one material onto the other
• plot and interpret voltage - current graphs for metallic conductors at constant temperature
• plot and interpret voltage-current graphs for a filament bulb
• Positive and Negative Charges
• recall and use the quantitative relationships between power, energy, current, voltage and time
• recall how the resistance of a thermistor (n.t.c.) varies with temperature
• recall that insulating materials can be charged by friction and explain this in terms of transfer of charge
• Repelling and Attracting
• state and use Ohm's Law in the form V/I = R, where R is the resistance
• The conductor will not experience a force if it is parallel to the magnetic field
• The direction of the force is reversed if either the direction of the current or the direction of the magnetic field is reversed
• The greater the charge on an isolated body the greater the potential difference between the body and earth
• The material that gains electrons becomes negatively charged
• The material that loses electrons is left with an equal positive charge
• The rate of flow of electrical charge is called the current
• The size of the force can be increased by: increasing the strength of the magnetic field, increasing the size of the current
• Two bodies that carry different types of charge attract
• Two bodies that carry the same type of charge repel
• understand that positively charged objects have a deficiency of electrons and negatively charged objects have a surplus of electrons
• understand that voltage is the energy transferred per unit charge
• Uses and dangers of electrostatic charges
• Uses of Electrostatic Charges
• Voltage (current) induced in a conductor and factors affecting its size
• Voltage is energy per unit charge
• When a conductor carrying an electric current is placed in a magnetic field, it may experience a force
• When certain insulating materials are rubbed against each other they become electrically charged
• When two electrically charged bodies are brought together they exert a force on each other