Electromagnetic Induction

• Created by: argyrou
• Created on: 01-05-18 21:37
When does electromagnetic induction occur?
when a wire cuts across lines of a magnetic field
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How do you increase an induced emf?
- moving the wire faster - using a stronger magnet - moving the wire into a coil and pushing the magnet in and out of the coil.
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How would you find the energy transferred per second from the source (power)?
Induced emf x current
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When/why is an emf induced?
there is relative motion between magnetic field and wire
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What do the different fingers signify in the right hand rule?
thumb = motion/velocity, first finger = field, 2nd finger = current
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What is the right hand rule used for?
Generators
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What is Lenzs law?
states that the direction of the induced current is always such as to oppose the change that causes the current.
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What is Faradays law of electromagnetic induction in words and as an equation?
States that the induced emf in a circuit is equal to the rate of change of flux linkage through the circuit. Induced emf=-N__/_t = -N_(BA)/_t
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What is the equation for magnetic flux _ and the unit?
BA (Wb - Weber)
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What is the magnetic flux linkage N_ and its unit?
BAN (Wb)
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What is the symbol for magnetic flux density and the unit?
B unit=Tesla T
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What equation would you use to find emf induced in a moving conductor in a magnetic field?
_=BLV
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What is the emf induced in a fixed coil in a changing magnetic field?
_=AN_B/_t
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What is the emf induced in a rectangular coil moving into a uniform magnetic field?
_=BNLV
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How would you work out the flux linkage of an alternating current generator?
BANcos(2_ft)
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How does the induced emf alternate according to what?
_=__sin(__t) where __=peak emf
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How can peak emf be increased?
-increasing speed - using a stronger magnet - bigger coil - more turns on the coil
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What is the equation for peak emf __?
__=BAN_
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What is back emf?
induced emf that acts against pd applied to the motor in accordance with lenzs law
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What is electrical power supplied by source equal to in words and as an equation?
electrical power supplied by source (IV) = electrical power transferred to mechanical power (I_) + electrical power wasted due to circuit resistance (I²R)
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How do you calculate the efficiency of an electric motor?
effiecieny=(mechanical power output/electrical power supplied)x100
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When observing alternating current, what happens to an oscilloscope waveform trace when you increase the output pd from the signal generator?
The trace becomes taller
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When observing alternating current what happens to the ocilloscope waveform trace when increasing the frequency of the signal generator?
Increases number of cycles on the screen
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How would you find the mean power over a full cycle for a sinusodial current?
Its half the peak power
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What is the definition of the root mean square value of alternating current?
The value of direct current that would give the same heating effect as the alternating current in the same resisitor.
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What is the equation to find the root mean square value of alternating current or pd?
RMS = (1/2)x peak value
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What is the transformer rule equation?
Vs/Vp=Ns/Np=Ip/Is
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How do you calculate the efficieny of a transformer (equation)?
efficiency=(IsVs/IpVp)x100
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In a step up transformer, what happens to voltage and current?
Voltage is stepped up, Current is stepped down
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In a step down transformer, what happens to the voltage and current?
voltage is stepped down, current is stepped up
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Other cards in this set

Card 2

Front

How do you increase an induced emf?

Back

- moving the wire faster - using a stronger magnet - moving the wire into a coil and pushing the magnet in and out of the coil.

Card 3

Front

How would you find the energy transferred per second from the source (power)?

Card 4

Front

When/why is an emf induced?

Card 5

Front

What do the different fingers signify in the right hand rule?