Course description
Overview
This course is targeted at Singapore Cambridge GCE O level students, but is also relevant to IGCSE students and Singapore's Integrated program students.
When you think of electricity, you might be imagining a current that flows from one point to another. That's direct current. The power in our houses, however, is very different. We use alternating current, which keeps on changing the direction it flows in. It turns out that there's a very good reason for doing so - distributing power to our houses would be much harder using direct current. But what does this have to do with electromagnetic induction? Join us and find out!
Course Content
You will learn:
- Why putting two coils of wire next to each other and running a current through one of them will cause them to jump
- How to generate electricity
- How to tweak alternating voltages to the values you want
- How to detect earthquakes using magnets
- Lots of other cool stuff!
A link to the full O level Physics syllabus can be found here
Course Prerequisites
You will need to know:
- How to watch videos on your computer
- It is encouraged that you complete the courses on Magnetism and Electromagnetism first. Familiart
Math Arena
The instructor is from Math Arena.The instructor is absolutely passionate about teaching and you'll find the lessons engaging and ultimately rewarding.
Course Curriculum
Moving a wire in a magnetic field
09:39
Q1 The wire XY shown in the diagram is connected to a sensitive voltmeter with a centre zero. XY is then moved quickly once through the magnetic field. What is observed on the voltmeter?
Q2 In the diagram below, a portion of a wire is being moved upward through a magnetic field. The current in the wire is directed towards point _____.
Q3 An electric potential difference will be induced between the ends of the conductor shown in the diagram below when the conductor moves in direction______.
Factors affecting the induced emf/current
13:16
Q4 The diagram below shows conductor C between two opposite magnetic poles. Which procedure will produce the greatest induced potential difference in the conductor?
Q5 The diagram below shows a copper wire located between the poles of a magnet. Maximum electric potential will be induced in the wire when it is moved at a constant speed toward which point?
Q6 The diagram below shows a wire moving to the right at speed v through a uniform magnetic field that is directed into the page. As the speed of the wire is increased, the induced potential difference will
Q7 The magnitude of the electric potential induced across the ends of a conductor moving in a magnetic field may be increased by
Q8 The e.m.f. induced in a conductor moving at right-angles to a magnetic field does not depend upon
Q9 A conductor is moving perpendicularly through magnetic field B as represented in the diagram above. If the magnetic field strength is doubled, the electric potential across the ends of the conductor will
Q10 The diagram below shows the cross section of a wire which is perpendicular to the page and a uniform magnetic field directed to the right. Toward which point should the wire be moved to induce the maximum electric potential?
Magnet-coil interactions
14:49
Q11 A magnet is pushed horizontally towards a coil of wire, inducing an e.m.f. in the coil. In which direction does the induced e.m.f. make the coil move?
Q12 A magnet is pushed slowly into a coil and there is a current in the coil in the direction shown. The magnet is then pulled out quickly from the same end of the coil. What happens to the direction and the size of the current?
Q13 A magnet is suspended from a spring so that it can move freely inside a coil which is connected to a sensitive centre-zero ammeter. What does the ammeter show when the magnet vibrates slowly up and down?
Q14 A coil connected to a galvanometer is placed near a fixed magnet. In order to produce an induced current as shown, what is the magnetic pole at Q and in which direction should the coil be moved?
Q15 A short bar magnet passes at a steady speed right through a long solenoid. A galvanometer is connected across the solenoid. Which graph best represents the variation of the galvanometer deflection 6 with time t?
Q16 A magnet is inserted into the centre of a coil and an e.m.f. is induced across the coil. The magnitude of the induced current depends on
Other interactions of conductors in a changing magnetic field
09:07
Q17 An aluminium ring hangs vertically from a thread with its axis pointing east-west. A coil is fixed near to the ring and coaxial with it. What is the initial motion of the aluminium ring when the current in the coil is switched on?
Q17 explanation
Q18 A copper ring is dropped over a bar magnet as shown in the figure. Which of the following statements about the induced current in the ring is correct?
Q19 An aluminium plate pivoted at P is allowed to swing into a magnetic field between a horseshoe magnet as shown. Which of the following is/are correct?
Rotating loops in a magnetic field
14:36
Q20 A conducting loop is rotating in a uniform magnetic field, causing an induced potential difference across the ends of the loop. As the speed of rotation of the loop increases, the induced potential difference
Q21 A conducting loop is rotating at a constant frequency between opposite poles of a magnet, causing an induced potential difference across the ends of the loop. As the two magnetic poles are moved farther apart, the induced potential difference
Q22 In the diagram below, a potential difference is induced in a wire loop as it is rotated between two magnetic poles. If the direction of the field is reversed and the speed of rotation is doubled, the maximum induced potential difference will be
Q23 The diagram at the right shows a wire loop rotating between magnetic poles. During 360º of rotation about the axis shown, the induced potential difference changes in
Q24 A wire loop is rotating between the poles of a magnet as represented below. As the loop rotates 90 degrees about the axis, the magnitude of the induced current in resistor R
The ac generator
16:30
Q25 The device used to convert mechanical energy into electrical energy is called
Q26 Which parts of an a.c. generator slide past each other when the generator is working?
Q27 The diagram shows an a.c. generator connected to an electrical circuit (load resistor). Which statement is correct?
Q28 Some changes are made, one at a time, to the ac generator shown in the following diagram. How many of these alter the value of the e.m.f. generated in the coil?
Q29 The graph shows the output of an a.c. generator. The coil in the generator rotates 20 times in one second. Which graph shows the output when the coil rotates 10 times in one second?
Reading the generator using a cathode-ray oscilloscope
06:27
Q30 A cathode-ray oscilloscope is connected to an a.c. generator. A wave is seen on the screen of the oscilloscope. The speed of rotation of the generator is doubled. What is the effect on the wave?
Q31 Graph X shows how the e.m.f output of an a.c generator varies with time. Graph Y shows the output from the same generator after a modification has been made to the generator. What was the modification made to produce the graph Y?
Q32 The diagram shows a voltage output waveform of an a.c generator as displayed on cathode-ray oscilloscope. If the frequency is 25 Hz and the voltage is 12 V, which one of the following shows the correct settings for the time-base and the Y-gain?
The transformer
44:01
Q33 The 200.-turn primary coil of a transformer is connected to a 120-volt line. How many turns must the secondary coil of the transformer have if it is to provide 240 volts? [Assume 100% efficiency.]
Q34 A transformer plugged into a 120-volt household electrical outlet is used to operate a 12V doorbell. What is the ratio of the number of turns in the primary coil to the number of turns in the secondary coil of the transformer?
Q35 A 100% efficient transformer has an 800.-turn primary coil connected to 120-volt alternating current source. If the secondary coil has 400 turns, what is the voltage induced in the secondary coil?
Q36 The diagram below shows a step-up transformer having a primary coil with two windings and a secondary coil with four windings. When a potential difference of 12V is applied to the primary coil, what is the current in an 8.0-ohm resistor?
Q37 The transformer on a power pole steps down the voltage from 10,800 volts to 120. volts. If the secondary coil contains 360 turns, how many turns are on the primary coil?
Q38 When a 12-volt potential difference is applied to the primary coil of a transformer, an 8.0-volt potential difference is induced in the secondary coil. If the primary coil has 24 turns, how many turns does the secondary coil have?
Q39 A transformer has 150 turns of wire in the primary coil and 1,200 turns of wire in the secondary coil. The potential difference across the primary coil is 110 volts. What is the potential difference induced across the secondary coil?
Q40 A transformer is designed to step 220 volts up to 2,200 volts. There are 200 turns on the primary coil. How many turns are there on the secondary coil?
Q41 In order for a transformer to function, its primary and secondary coils must
Q42 An ideal transformer has a current of 2.0 amperes and a potential difference of 120 volts across its primary coil. If the current in the secondary coil is 0.50 ampere, the potential difference across the secondary coil is
Q42 explanation
Q43 In a transformer, two coils of wire are wound around a common iron core. To operate properly, the transformer requires
Q44 The primary coil of an operating transformer has 200 turns and the secondary coil has 40 turns. This transformer is being used to
Q45 Which arrangement may be used to step up a voltage?
Q46 The diagram shows a working transformer. Which statement is correct?
Q47 A transformer is to be used to produce a 6 V output from a 24 V input. What are suitable numbers of turns for coil X and for coil Y?
Q48 A transformer is to be used to provide a 10 V output from a 100 V supply. What are suitable numbers of turns for the primary coil and for the secondary coil?
Q49 A transformer has 50 turns on its primary coil and 100 turns on its secondary coil. An alternating voltage of 25.0 V is connected across the primary coil. What is the voltage across the secondary coil?
Q50 The diagram shows a transformer connected to a 240 V a.c. supply. What is the potential difference across the secondary coil of the transformer?
Q51 A transformer has 15 000 turns on its primary coil and 750 turns on its secondary coil. Connected in this way, for what purpose could this transformer be used?
Q52 The diagram shows a transformer operating a door bell The mains supply of 240 V is connected to the transformer. The bell has a resistance of 8.0 Ω and the output voltage from the transformer is 12 V. What is the current drawn from the mains supply?
Q53 An alternating current flows through coil P. Coil Q is connected to a C.R.O. on which a sinusoidal trace appears. What happens to the trace if P and Q are linked by a soft-iron core?
Q54 The graph shows the voltage input to a step-down transformer. Which diagram shows the voltage output from the transformer?
Q55 Electric power cables transmit electrical energy over large distances using a high voltage, alternating current. What are the advantages of using a high voltage and of using an alternating current?
Q55 explanation
Structured Questions Bundle A
43:36
SQ1 (part 1) Rotating magnet generator explain how alternating current is produced
SQ1 (part 2) Rotating magnet generator transformer calculations
SQ2 Ring-shaped transformer connected to light bulb
SQ3 Ring-shaped transformer connected to ammeter
SQ4 Turning coil generator
SQ5 Induction seismometer
SQ6 Transformer with a turns ratio of 1:50
SQ7 (part 1) Induction seismometer 2 explaining pd
SQ7 (part 2) Induction seismometer 2 motion of the magnet
SQ8 (part 1) Turning coil generator 2 operation of the generator
SQ8 (part 2) Turning coil generator 2 graphing the emf
SQ8 (part 3) Turning coil generator 2 connecting the generator to a transformer
Structured Questions Bundle B
38:24
SQ9 C-core transformer
SQ10 Sliding copper rod
SQ11 (part 1) Sliding magnet into solenoid explaining galvanometer deflection
SQ11 (part 2) Sliding magnet into solenoid right-hand-grip rule
SQ12 Anemometer
SQ13 Electric guitar pick-up
SQ14 (part 1) Campsite generator step-down transformer
SQ14 (part 2) Campsite generator step-up transformer
SQ15 (part 1) Turning coil generator 3 functions of different parts
SQ15 (part 2) Turning coil generator 3 direction of current flow
SQ15 (part 2) explanation
SQ15 (part 3) Turning coil generator 3 graph of one complete turn
SQ15 (part 4) Turning coil generator 3 graphs after changing various factors
Structured Questions Bundle C
38:21
SQ16 (part 1) Single-core double solenoid deflection and repulsion
SQ16 (part 2) Single-core double solenoid observations on opening the switch
SQ17 (part 1) Rectangular transformer magnetic field pattern
SQ17 (part 2) Rectangular transformer graphs
SQ18 3300-turn transformer
SQ19 40W transformer
SQ20 (part 1) Transmitting electricity pd and current calculations
SQ20 (part 2) Transmitting electricity power calculations
SQ21 (part 1) Transmitting electricity 2 power in distribution cables
SQ21 (part 2) Transmitting electricity 2 power in transmission cables
SQ22 Using alternating voltages
SQ23 Horseshoe core