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25 Cards in this Set
- Front
- Back
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What is a Voltage Divider? |
A Voltage Divider, is a network of resistors which develop a lower voltage, from the higher voltage power supply. |
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What is the Voltage Divider Equation? |
Vout= (R2/R1+R2) X Vin |
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What are 6 ways of producing a EMF? |
1. Magnetism. Ex. Alternator. 2. Chemical. Ex. Batteries/Fuel cells. 3. Friction. Ex. Van der Graff generator. 4. Light. Ex. Solar cells. 5. Heat. Ex. Thermocouple. 6. Pressure. Ex. Piezo crystal |
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List the parts of a DC Motor |
1: Coil Armature 2: North and South magnets 3: Split Ring Commutator 4: Carbon Brushes |
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What is the function of a Commutator? |
A Commutator purpose is to reverse the current direction. This stops the Armature from changing direction, to oppose the magnetic field. Which produces a steady torque in one direction. |
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What is a permanent Magnet? |
A magnet that retains its magnetic properties in the absence of an inducing field or current. |
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What is Magnetic flux? |
Magnetic Flux, Phi, is a measure of the amount of Magnetism, and can be measured by lines of Magnetic Flux. Its unit is the Weber (WB). |
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What is Flux Density? |
Magnetic flux density is the amount of flux lines per unit area. It's symbol is B. |
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What is a Temporary Magnet? |
A temporary magnet, is a magnet which loses its magnetism, when the magnitising force is removed. |
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What are the lines of force? |
An imaginary line which represents the strength and direction of a magnetic, gravitational, or electric field at any point. |
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What are the Poles of a Magnet? |
Magnets have two poles, they are north pole (N) and south pole (S). These poles are present at each end of a magnet. Same Poles rebel and opposites attract. |
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What is a Magnetic Field? |
A region around a magnetic material or a moving electric charge within which the force of magnetism acts. |
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What are the components of a D.C motor? |
1)Armature 2)Commutator 3)Brushes 4)Axle 5)Stationary Magnets 6)DC power supply of some (where the EMF is stored) |
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How does a DC generator work? |
When a mechanic force rotates the Armature, it moves through the magnetic field. This induces a EMF in the conductive armature. Creating a voltage output. |
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State Faraday's Laws of Electromagnetic Induction. |
1) An induced EMF is established in a circuit, whenever the magnetic field linking to the circuit changes. 2) The Magnitude of the induced EMF, is proportional to the rate of change, of the magnetic flux linking it. |
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What is Lenz's law of Electromagnetic Induction? |
The induced EMF, acts in a direction, which opposes the change in flux that is causing the EMF to be induced. |
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How does a Loud Speaker work? |
When a fluctuating electric current flows through a coil, it becomes a temporary electromagnet, attracted and repelled by the permanent magnet. As the coil moves, it moves the cone back and forth, pumping sound waves into the air. |
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What is Fleming's Left Hand rule? |
Fleming's Left Hand Rule, is used to discover the direction of the Force acting on the conductor. The thump represents the direction of the Force, the index finger the flux lines and the middle finger the direction of current. |
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What is the Right Hand Grasp rule? |
The right-hand grip rule is used to determine the relationship between the current and the magnetic field. The thump points in the direction of current flow, and the fingers curl and point in the direction of the magnetic field. |
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How does a relay work? |
Relays control one electrical circuit by opening and closing contacts in another circuit. When the relay is triggered, a current passes through the electromagnet, attracting the Armature and contacting the contacts, completing the other circuit. |
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How does a electric doorbell work? |
When an electric current flows through the coils, the rods become magnetic and attract a piece of iron attached to a clapper. The clapper hits the bell and makes it ring. When the armature leaves it's start point, it breaks a set of contacts, which break the circuit, this stops the magnet working, so the clapper falls back to it's start point and begins the process again. |
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How does a Moving Coil Instrument work? |
A meter consists of a set of opposing magnets, with a wire coil attached to a needle. The wire coil has a wire attached on each end. When a electric current passes down the wire it magnetises the needle which makes the needle flick to one side, the side and amount is depend on the size and direction of the current flow. |
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How does a Lifting magnet work? |
A Lifting magnet is just a very large temporary magnet. It consists of a large iron disk, which is attached in a circuit. When the power is turned on, and current flows through the disk, it magnetises the iron, creating a powerful magnet. |
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How does a Electric door lock work? |
Electric door locks work simply, by using an electromagnet to attract to a metal plate on a door. They can be used to hold fire doors open and release them when the alarm goes off. |
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Explain how a Transformer Works |
A transformers purpose is to reduce the amount of voltage. It works by having a iron core, on which 2 separate coils are attached. A high voltage AC flows through the first coil called the "Primary Coil". When this happens a Magnetic Field is produced. Coursing a induced current of a lesser voltage on the "Secondary coil". This induced voltage is now safe to run our household appliances. |
