4.5. Electromagnetic effects
A subsection of Physics, 5054, through 4. Electricity and magnetism
Listing 10 of 237 questions
A vertical solenoid (long coil) with an iron core is held in a wooden clamp above a laboratory bench. The solenoid is connected in series with a battery, a switch S, an ammeter and a variable resistor. There is a voltmeter in parallel with the solenoid. represents this apparatus. V A S battery iron core solenoid A student closes switch S and a current in the circuit produces a reading on the ammeter. State what is meant by current. The battery consists of five 1.5 V cells in series. The reading on the ammeter is 4.0 A. State the size of the electromotive force (e.m.f.) of the battery. Calculate the total resistance of the series circuit. resistance = The reading on the voltmeter is 6.5 V. Calculate the power dissipated in the solenoid. power = The solenoid is made of copper and the student notices that, as time passes, the solenoid becomes extremely warm. State and explain the effect of this temperature increase on the ammeter reading. The current in the solenoid magnetises the iron core so that the lower end of the core is an N-pole. On , draw the pattern and indicate the direction of the magnetic field in the region surrounding the iron core. The student holds an iron cylinder against the bottom surface of the iron core in the solenoid. When he releases the iron cylinder, it stays in contact with the iron core. 1. Explain why the iron cylinder does not fall. 2. The switch S is opened. State and explain whether the iron cylinder remains in contact with the iron core.
5054_w16_qp_22
THEORY
2016
Paper 2, Variant 2
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An electric circuit consists of a battery, a variable resistor and connecting wires. Sections PQ and QR of the connecting wire are in a region of space where there is a uniform magnetic field. In , the shaded area represents the magnetic field. uniform magnetic field into the page P Q R The direction of the magnetic field is into the page. A current-carrying wire in a magnetic field can experience a force. In the table, mark one tick (✓) in each column to indicate the force on PQ and the force on QR. section PQ section QR no force on this section a force towards the top of the page a force towards the bottom of the page a force out of the page a force into the page a force towards the left of the page a force towards the right of the page The battery in the circuit in is reversed. State and explain the effect of this on PQ and QR. The variable resistor is adjusted and the current in the circuit decreases. Suggest one effect of decreasing the current.
5054_w17_qp_21
THEORY
2017
Paper 2, Variant 1
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An a.c. generator produces alternating current. Draw a labelled diagram of a simple a.c. generator. Explain how the current is generated. The output of the generator is connected to the terminals of a cathode-ray oscilloscope. shows the trace produced on the screen of the oscilloscope. trace 1 division Each vertical division on the scale in represents 2 volts. Describe how you would check that one vertical division represents 2 volts. The trace in is too small and is at the bottom of the screen. Adjustments are made to the oscilloscope controls to produce the trace in . State and explain the adjustments made to the oscilloscope controls. Explain how the beam of electrons is produced inside the cathode-ray oscilloscope.
5054_s09_qp_2
THEORY
2009
Paper 2, Variant 0
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shows a rotating magnet in an alternating current generator that is used to power a lamp. coil lamp soft iron magnet N S State how an alternating current differs from a direct current. Explain, in detail, how alternating current is produced by the apparatus shown in . State two ways in which the current in the lamp may be increased. 1. 2. The generators at a power station produce a voltage of 25 000 V. This voltage is stepped up to 400 000 V by a transformer for long-distance transmission on overhead power lines. The voltage is later stepped down to 240 V. State and explain why the voltage is stepped up for long-distance transmission. Calculate the ratio of the number of turns in the primary coil of the step-up transformer to the number of turns in its secondary coil. ratio = State one advantage and one disadvantage of using thicker wire in the overhead power lines. advantage: disadvantage: An electric drill of power 1000 W is used in a country where the mains voltage is 240 V. State and explain the most appropriate fuse to use with this drill. You should select a fuse from the following values: 1 A, 3 A, 4 A, 13 A.
5054_s11_qp_21
THEORY
2011
Paper 2, Variant 1
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shows a coil of wire connected by flexible leads to a switch and a battery. FRLO IOH[LEOH OHDG IOH[LEOH OHDG EDWWHU\  ² VZLWFK D[LV The coil is placed between the poles of a permanent magnet and is free to turn about the axis. When the switch is closed, forces due to the current act on the sides of the coil. The coil starts to turn. On , draw arrows to show the directions of the forces. The coil stops when it is vertical. Explain why the turning effect of the forces is zero at this position. In order for the coil to rotate continuously, a split-ring commutator is connected between the battery and the coil. Explain how the split-ring commutator enables the coil to rotate continuously. Include a diagram in your answer.
5054_s14_qp_21
THEORY
2014
Paper 2, Variant 1
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Questions Discovered
237