IB PHYSICS > 12 Electromagnetic Induction
1 Measure
2 Mech
3 Therm
4 Waves
5 Electric
6 Fields
7 Atomic
8 EPCC
9 MIF
10 Therm AHL
11 Wave Phen
12 EMI
13 QNP
14 Digital
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TRANSMISSION OF ELECTRIC POWER


IDEAL TRANSFORMER: A device which induces in a secondary coil an emf by variation of an emf in the primary coil. It is ‘ideal’ if the efficiency is 100%.
Outline the reasons for power losses in transmission lines and real transformers.

REAL TRANSFORMER: Energy losses are due to heating of the wires; magnetic flux linkage less than 100%; heating due to changing magnetic field (hysteresis); heating due to eddy currents.

AC TRANSMISSION: Since energy losses are proportional to current2, it is important to reduce current which is achieved by increasing PD. Step-up transformers do this and therefore, transmission uses AC with a frequency of 50Hz.

Explain the use of high-voltage step-up and step-down transformers in the transmission of electrical power.
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Solve problems on the operation of real transformers and power transmission.

Students should be aware that, for economic reasons, there is no ideal value of voltage for electrical transmission

Suggest how extra-low-frequency electromagnetic fields, such as those created by electrical appliances and power lines, induce currents within a human body.

HEALTH RISKS: Alternating currents produce changing electric and magnetic fields which will induce emfs in conductors. There is a hypothesis that this may cause genetic damage. The effect could depend on current, frequency and exposure time.
Discuss some of the possible risks involved in living and working near high-voltage power lines.

Students should be aware that current experimental evidence suggests that low‑frequency fields do not harm genetic material. Students should appreciate that the risks attached to the inducing of current in the body are not fully understood. These risks are likely to be dependent on current (density), frequency and length of exposure.