The diagram shows the magnetic field around a solenoid carrying an electric current. What happens to the strength of the magnetic field and the distance between the field lines when the current is increased?
A.
B.
C.
D.
Exam No：0625_s23_qp_23 Year：2023 Question No：29
Answer:
C
Knowledge points:
4.1.1 Describe the forces between magnets, and between magnets and magnetic materials
4.1.10 Describe methods of demagnetisation, to include hammering, heating and use of alternating current (a.c.) in a coil
4.1.2 Give an account of induced magnetism
4.1.3 Distinguish between magnetic and non-magnetic materials
4.1.4 Describe methods of magnetisation, to include stroking with a magnet, use of direct current (d.c.) in a coil and hammering in a magnetic field
4.1.5 Draw the pattern of magnetic field lines around a bar magnet
4.1.6 Describe an experiment to identify the pattern of magnetic field lines, including the direction
4.1.7 Distinguish between the magnetic properties of soft iron and steel
4.1.8 Distinguish between the design and use of permanent magnets and electromagnets
4.1.9 Explain that magnetic forces are due to interactions between magnetic fields
4.6.1.1 Show understanding that a conductor moving across a magnetic field or a changing magnetic field linking with a conductor can induce an e.m.f. in the conductor
4.6.1.2 Describe an experiment to demonstrate electromagnetic induction
4.6.1.3 State the factors affecting the magnitude of an induced e.m.f.
4.6.1.4 Show understanding that the direction of an induced e.m.f. opposes the change causing it
4.6.1.5 State and use the relative directions of force, field and induced current
4.6.2.1 Distinguish between d.c. and a.c.
4.6.2.2 Describe and explain a rotating-coil generator and the use of slip rings
4.6.2.3 Sketch a graph of voltage output against time for a simple a.c. generator
4.6.2.4 Relate the position of the generator coil to the peaks and zeros of the voltage output
4.6.3.1 Describe the construction of a basic transformer with a soft-iron core, as used for voltage transformations
4.6.3.2 Recall and use the equation
4.6.3.3 Understand the terms step-up and step-down
4.6.3.4 Describe the use of the transformer in high- voltage transmission of electricity
4.6.3.5 Give the advantages of high-voltage transmission
4.6.3.6 Describe the principle of operation of a transformer
4.6.3.7 Recall and use the equation $I_{p} V_{p}=I_{s} V_{s}$(for 100% efficiency)
4.6.3.8 Explain why power losses in cables are lower when the voltage is high
4.6.4.1 Describe the pattern of the magnetic field (including direction) due to currents in straight wires and in solenoids
4.6.4.2 Describe applications of the magnetic effect of current, including the action of a relay
4.6.4.3 State the qualitative variation of the strength of the magnetic field over salient parts of the pattern
4.6.4.4 State that the direction of a magnetic field line at a point is the direction of the force on the N pole of a magnet at that point
4.6.4.5 Describe the effect on the magnetic field of changing the magnitude and direction of the current
4.6.5.1.1 the current
4.6.5.1.2 the direction of the field
4.6.5.2 State and use the relative directions of force, field and current
4.6.5.3 Describe an experiment to show the corresponding force on beams of charged particles
4.6.6.1.1 increasing the number of turns on the coil
4.6.6.1.2 increasing the current
4.6.6.1.3 increasing the strength of the magnetic field
4.6.6.2 Relate this turning effect to the action of an electric motor including the action of a split-ring commutator
Solution:
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