7 Fig. 7.1 shows part of a torch. The torch does not contain a battery. N S coil magnet Fig. 7.1 The torch is shaken and this causes the magnet to move backwards and forwards throu... 7 Fig. 7.1 shows part of a torch. The torch does not contain a battery. N S coil magnet Fig. 7.1 The torch is shaken and this causes the magnet to move backwards and forwards through the coil. (a) (i) Explain why an electromotive force (e.m.f.) is induced in the coil when the magnet moves. (ii) State one way to increase the e.m.f. induced. (b) The current in the coil is used to produce light from a light-emitting diode (LED). (i) In the space below, draw the circuit symbol for an LED. (ii) An LED is a more efficient source of light than a filament lamp. Explain what this statement means.
Understand the Problem
The question is asking about the principles of electromotive force (e.m.f.) induction when a magnet moves through a coil, methods to increase e.m.f., and the comparison of LED efficiency to filament lamps. The response involves explanations of electromagnetic induction and properties of LEDs.
Answer
Movement of the magnet through the coil changes the magnetic field, inducing e.m.f. due to Faraday's Law. To increase e.m.f., move the magnet faster or use a stronger magnet. LEDs are more efficient, converting more electricity to light than heat.
When the magnet moves through the coil, it changes the magnetic field within the coil. According to Faraday's Law of Electromagnetic Induction, this change induces an electromotive force (e.m.f.) in the coil. To increase the e.m.f., you can either move the magnet faster, use a stronger magnet, or increase the number of turns in the coil. An LED, being more efficient than a filament lamp, means it converts more electrical energy into light rather than heat.
Answer for screen readers
When the magnet moves through the coil, it changes the magnetic field within the coil. According to Faraday's Law of Electromagnetic Induction, this change induces an electromotive force (e.m.f.) in the coil. To increase the e.m.f., you can either move the magnet faster, use a stronger magnet, or increase the number of turns in the coil. An LED, being more efficient than a filament lamp, means it converts more electrical energy into light rather than heat.
More Information
The movement of magnets inducing electricity is the principle behind many electricity generation systems, such as dynamo generators in bicycles or large-scale generators in power plants.
Tips
A common mistake is not accounting for the strength of the magnetic field or the speed of movement, both of which are crucial for inducing a sufficient e.m.f.
Sources
- CIE, O Level, Physics, 5054/21, Jun19 - Papers - papers.xtremepape.rs
- Solved 1 Fig. 3.1 shows the design of a 'mechanical' torch. - Chegg - chegg.com
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