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Physics

Magnetism and Electromagnetism

QuestionAnswer
How do you increase the strength of a magnetic field around a solenoid? Adding a magnetically soft iron core
Why is iron used in transformers? It needs to magnetise and demagnetise quickly
What is the definition of electromagnetic induction? The creation of voltage in a wire which is experiencing a change in magnetic field
How do you get a bigger voltage when testing the dynamo effect? 1. Increasing strength of magnet 2. Increasing number of turns on the coil 3. Increasing the speed of movement
In an A.C generator, the current ______________________ every half turn Changes direction
As a coil spins in an A.C. generator, current is ____________ Induced
In an A.C. generator, faster revolutions produce _________ and ____________ on a CRO display More peaks, higher overall voltage
What is the equation for power? Power = Voltage x Current
What is the equation for input power = output power? Vp Ip = Vs Is
What is the transformer equation? Vp/Vs = Np/Ns
How do you test the strength of an electromagnet? By picking up paper clips
What is an example of a magnetically soft material? Iron
What is an example of a magnetically hard material? Steel
What does it mean if a material is magnetically soft? It loses its induced magnetism quickly
What does it mean if a material is magnetically soft? It keeps its induced magnetism permenantly
To experience full force of the motor effect, a wire has to be at _____________ to the magnetic field 90 degrees
The force during the motor effect increases with the strength of the _______________ and the amount of __________ there is magnetic field, current
In the motor effect, what will happen to the direction of the force if the current or magnetic field is reverse It will also reverse
What 4 factors will speed up a simple D.C. motor 1. More current 2. More turns on the coil 3. Stronger magnetic field 4. A soft iron core in the coil
What does a split-ring commutator do? Swap the positive and negative electrical contacts every half turn, so the motor keeps rotating in the same direction
How does the motor effect cause loudspeakers to work? 1. A.C. signals from amplifier are fed to coil of wire in the speaker at the base of cone 2. Permanent magnet surrounds coil, making A.C. signals cause force on the coil, causing it to move back and forth 3. Movements make cone vibrate, creating sounds
Created by: JoeMather
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