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Electricity
AS91173 - 2.6
Question | Answer |
---|---|
Charge Basics | Opposite charges attract, like charges repel. |
Electrons | Lowest possible negative charge. |
Charging by Induction | No physical contact, once rod is removed the electroscope stays neutrally charged. |
Charging by Conducion | Physical contact, once rod is removed the electroscope remains charged. |
Electric Fields | A region in which a charged object experiences a force - shape will depend on surrounding objects. |
Protons | Lowest possible positive charge. |
Electric Field Lines | Intersect charged objects at 90, seperation between lines shows strength, lines go from positive to negative charges and will never touch one another. |
Forces on Charge | The electric force is always parallel to the electric field lines with the field lines pointing in the direction that the positive charge moves in. |
Forces on Charge - Parabolic Paths | If a charge is travelling horizontally then enters an electric field, the charge will travel in a parabolic path. Horizontal velocity will be unaffected, however vertical velocity will increase. |
Electrostatic Potential Energy | The energy stored within an electric field, when energy is used to push against a force it will gain potential energy as well as having work done. |
Energy Transfer | Energy cannot be destroyed or created, only transfered. |
Current | Flow of electrons, the amount of charge that passes a certain point per second. |
Electrical Circuits | Consist of a power source, have an unbroken pathway and electrical components which use or control energy. |
Conventional Current | Assumes current flows out of the positive terminal and towards the negative terminal. |
Electrical Charge | Total charge - Q, individual charge - q, measured in Coulombs. |
Electrical Current | Flow of electrons from on place to another, how much charge passes a point per second. Symbol - I, units - Amps (A). |
Voltage | How much energy per charge, the speed of charge, symbol - V, units - J/C or V. |
Reistance | The slowing of electrons as they floow through a conductor or the measure of how much a component opposes the flow of electrons through itself. |
Series Ciruits | Current is constant, resistance and voltage is shared so that it adds to the total. |
Parallel Circuits | A branch's current adds up to the total current entering the parallel block, each branch uses identical voltage to other branches and 1/Rtot = 1/R1 + 1/R2 |
Brightness of Lamps | Lamps convert electrical energy to light and heat energy, the brighter the lamp the more energy it converts. The rate of conversion is power. |
Shorting Lamps | Placing a wire in parallel with a lamp sorts it. All the current will flow through the wire which means no current flows through the lamp, it will use no voltage, draw no power and will not glow. |
Blowing Bulbs | Lamps are designed to operate at a certain voltage. They can only handle slightly more voltage (~20%) but after that the blub will burn out (filament melts). |
Power | The rate at which electrical energy is converted into other forms of energy. |
The Voltage Divider | Used when a power supply provides more voltage than an appliance requires and made by placing two resistors with connections to the appliance in series. |
Ohmic Conductors | These will obey Ohms Law and will have constant resistance for all voltage/current reading (produces linear graphs). |
Non-Ohmic Conductors | These don't obey Ohms Law and change their resistance as voltage/current changes (non-linear graphs are produced). |
Diodes | Allows current to pass in only one direction and are used to control the direction of current flow. |
Magnet Makeup | Made from ferromagnetic substances, contain magnetic domains. |
Magnetic Domains | These are the north (negative) and south (positive) poles on a magnet, In non-magnetised objects the magnetic domains are arranged randomly and poles cancel out. The more domains aligned, the stronger the magnet. |
Magnetic Fields | Three dimensional, can be produced by current in a conductor. May be circular due to concentric circles spreading out from a conductor. |
Magnetic Field Lines | Run from north to south, arrive and leave magnetcs at right angles to the surface. Show the magnetic field is stronger when lines are closer. |
Right-Hand Grip Rule | Point the THUMB in the direction of the CURRENT, FINGERS curl in the direction of the MAGNETIC field. |
Magnetic Fields Around Parallel Wires - Current in Opposing Directions | Creates magnetic fields that repel each other, the wire will experuence a repulsive force. |
Magnetic Fields Around Parallel Wires - Current in the Same Direction | Creates magnetic fields that attract each other, the wire will experience an attractive force. |
Right-Hand Slap Rule | THUMB in the direction of CURRENT, FINGERS in the direction of the MAGNETIC FIELD, PALM in the direction of LORENTZ FORCE. |
Magnetic Forces | A current carry conductor in a magnetic field will experience a force as the magnetic fields interact with each other. |
Right-Hand Slap Rule for Force | THUMB in direction of CONVENTIONAL CURRENT, FINGERS in direction of EXTERNAL MAGENTIC FIELD, PALM points towards MOVEMENT or FORCE EXERTED ON CONDUCTOR. |
Charged Particles in Magnetic Fields | Will experience a force that is perpendicular to the velocity of the charge and magentic field. That force can only influence direction so that the particle travels in a circular path. No work is done and there will be no force on a stationary particle. |
Conventional Current | The flow of positive charges. |
Right-Hand Slap Rule for Induced Current | FINGERS point in the direction of the EXTERNAL MAGNETIC FIELD, THUMB points in direction of the PARTICLE’S MOTION, PALM points in the direction of the LORENTZ FORCE. |
Solenoids | Formed whem a straight wire is wound into a circular coil, when current flows through a magnetic field forms, the strongest of which is in the centre of the solenoid. |
Right-Hand Grip Rule for Solenoids | THUMB points to the NORTH POLE, FINGERS curl in the direction of CURRENT. |
Increasing Strength of Eletcromagnets | Increase voltage and number of coils, insert an iron core. |
Electromagnetic Induction | Current is induced and work is being done by moving a conductor through a magnetic field. |
Right-Hand Slap Rule for Induction | THUMB in the direction of the MOTION of the POSITIVE CHARGE PARTICLE, FINGERS in the direction of EXTERNAL MAGNETIC FIELD, PALM in the direction of LORENTZ FORCE. |
Generator Effect | Moving Conductor + magnetic field = induced current. |
Induced Voltage | Produced when a length of wire is moved across a magnetic field, creates a a force against motion and work is being done. |
Loops Moving Through Magnetic Fields | No part of the loop in field – no voltage induced, one side in field – voltage on that side (acts as power supply), current flows around loop, entire loop within field – all sides have voltage but no current (positives and negatives cancel out). |
Forces Against Motion | When voltage is induced a force that opposes the motion is produced, this force resists motion because kinetic energy is being converted into electrical energy. |