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level: Level 1

Questions and Answers List

level questions: Level 1

QuestionAnswer
How does the magnetic field outside of the coil of a solenoid actLike a normal bar magnet (round from North to South)
How does the magnetic field outside of the coil of a solenoid actLike a normal bar magnet (round from North to South)
What does a current carrying wire haveIt contains as a magnetic field as its an electromagnet
Drawing of a magnetic field around a straight current-carrying wireDiagram
What is the Right Hand Thumb RuleUsing your right hand, point your thumb in the direction of the current, and curl your fingers. The direction of your fingers is the direction of the field.
Diagram of the Right Hand Thumb RuleDiagram
Factors affecting the strength of the magnetic fieldIf current increases, magnetic field strength increases (Current directly proportional) The closer you are to the wire, the stronger the magnetic field strength (Distance inversly proportional)
What is a solenoidWrapping a wire into a coil to increase the strength of the magnetic field
How to increase the magnetic strength of a solenoidWrap the coil around a piece of iron (Iron becomes induced and combined magnetic field is stronger) Adding more turns to the solenoid (field lines closer so stronger) Increase current flowing through the coil
What does the magnetic field of a solenoid look likeDiagram
What direction does the magnetic field in a solenoid go towardsFrom N to S like a normal Magnet
How does the magnetic field inside of the coil of a solenoid actActs uniform (same direction adn strength at every direction)
How does the magnetic field outside of the coil of a solenoid actLike a normal bar magnet (round from North to South)
Uses of electromagnetsSince you can turn on and off a electromagnet It is useful for switches (Electric Bell) For magnets on cranes at scrapyards
How to determin where N and S is in a solenoidIf the coil is anticlockwise, it is North pole If the coil is clockwise, it is South pole
What is the Motor effectWhen a current carying wire (electromagnet) is placed in a magnetic field of two magnets (N to S), the wire experiences a force
What is the Left hand Flemming RuleF (Force) [Thumb] B (magnetic flux density) [Index] I (Current) [Middle]
Calculating the size of the forceF = BIL F = force (Newtons) [N] B = magnetic flux density (Tesla) [T] I = Current (Amps) [A]
Components of a Simple dc electric motorA Motor with a loop of wire inbetween the two magnets A DC current The force acts downwards and the wire turns vertical and gets stuck as it cannot rotate anymore. The split ring commutator reverses the direction of the current and makes the rotation continue A split ring commutator is just a conducting ring with a gap between the two halves. As it rotates, the part of the commutator that is touching each contact chagnes every half turn.
Diagram of a Simple dc electric motorDiagram
How to increase speed of simple dc electric motorBy increasing the Current By increasing the strength of the magnetic field Using a coil instead of a single loop of wire
How to change direction of a simple electric motorSwapping the polarity of the direct current supply Swapping the magnetic poles
Components of a LoudspeakerDiagram
Explanation of a loudspeakerThe AC current in the loudspeaker means the wire moves clockwise then anticlockwise tonnes of times, causing vibrations in the air pressure causing sound waves to be formed Controlling AC frequency will generate different sound waves.
What is a Generator effectThe generator effect is the induction of a potential difference (and current if there's a complete circuit) across a conductor which is experiencing a change in an external magnetic field
The potential difference can be induced through 2 waysMoving the electrical conductor in a magnetic field Or Moving or changing a magnetic field relative to the electrical conductor
When is a current produced in the generator effectWhen it is a complete circuit that is being used in the generator
Creating a generator effect with a coil and a permanent magnetThe permanent magnet rotates in the coil or The permanent magnet moves forwards and backwards in and out
What happens to the electromagnet/wire when the wire stops moving or changes direction of movement (up and down, left and right)Potential difference dissapears when stopped moving The direction of the potential difference (negative and positive) swaps each time we swap direction
How to change the size of the induced potential differenceChanging the strength of the magnetic field (stronger magnets), so theres a larger potential difference move the wire, or magnets more quickly so the magnetic field will change more, so its a bigger potential difference Shape the wire into a coil so there are more turns so the field lines are closer so tehre is a bigger potential difference
Image of generator effectDiagram
Difference between generator and motor effectMotor effect has current already, generator effect generates pd and current from 0
What is an alternatorAn alternator genrates alternating current and every half turn done, the pd and current changes direction but the slip rings and brushes on the alternator makes it so the contacts dont swap every half term. This will mean they collect AC rather than DC
What is a DynamoAn dynamo generates DC using a split ring commutator that does swap the contact point every half turn.
Why doesnt a generator's wire move without human inputAs it has no current to do motor effect. The structure of the circuit and magnets are the same, but current isnt there for generator and is there for motor. A motor uses current to exert force A generator uses force to generate current
What is an oscilloscopeA device used to see the generated potential difference.
What is the x and y axis on a oscilloscopeX axis = Time Y axis = Voltage
How do you increase the peak of the trace cycle in the oscilloscope of the generator effectIncreasing the frequency of rotations in the generator. This would also squash the trace cycle horizontally.
How do you enlarge the entire wave of the trace cycle in the oscilloscope of the generator effectby increasing the strength of the magnetic field
What does a direct PD trace cycle look likeImage
How do microphones workMicrophones generate current from sound waves Sound waves hit a flexible diaphragm that is attached to a coil of wire wrapped around a magnet. The sound waves causes the coil of wire to move back and forth in the magnetic field which generates a current. The movement of the coil depends on the proeprties of the sound wave that hits the flexible diaphragm This is how microphones can convert the different sound waves into variations in current in a circuit
Diagram of microphoneDiagram
What is the basic structure of a transformerConsists of two coils, the primary and the secondary, wrapped around an iron core. Iron is used for the corea because it can magnetise and demagnetise quickly
Diagram of the basic structure of a transformerDiagram
How does a transformer workWhen an AC flows through the primary coil in a transformer it produced a magnetic field which magnetises the iron core Due to the AC, the magnetic field in the iron core alternates. This constantly changing field cuts through the secondary coil The changing field induces an alternating potential difference across the ends of teh secondary coil by the generator effect If the secondary coil is part of a complete sicruit, this pd causes an ac to flow, it has the same frequency as the atlernating current in the primary coil
What does the size of the pd at the secondary coil depend onSize of the pd across the primary coil Number of turns on each coil
Remember this about transformersIt doesnt carry charge from the first coil to the second. The magnetic field does this
Why wont you get any significant pd or current at the secondary coil if there is DC put into primary coilThere wont be a constant changing force to cut the secondary coil's magnetic field and make a pd
What are step up and step-down transformersThey change an electrical supply so that the size of the output pd is not the same as the input pd
Ratio between the primary and secondary pd compared to the ratio of number of turns on the priamry coil and secondary coilThe ratio of First coil PD: Second coil PD is the same as Number of turns in First Coil: Number of turns in the Second Coil
A step up transformerTHe number of turns on the secondary coil and the size of the pd across it are greater than across the primary coil
A step down transformerThe number of turns on the secondary coil and the size of the pd across it are bigger than across the primary coil
Where are step up and step down transformers used inThe national grid Step up increase pd of the supply for transmission around the country via power lines This means the current is lower meaning less energy is lost in heating.