Electromagnetic InductionEdexcel IGCSE Physics: Flashcards
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What is electromagnetic induction?
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- What is electromagnetic induction?
- The production of a voltage in a conductor caused by a changing magnetic field around it (e.g. from relative movement between a conductor and a magnet).
- Name two ways to induce a voltage in a coil.
- Move the coil (or a magnet) so the coil experiences a changing magnetic field; or change the magnetic field through a stationary coil.
- Name three factors that increase the size of an induced voltage.
- Moving faster, using a stronger magnet, and using a coil with more turns.
- How does a generator produce electricity?
- By rotating a magnet within a coil of wire, or a coil of wire within a magnetic field, continuously inducing a voltage.
- Why do generators produce alternating current?
- Because the rotation continuously reverses the direction of the changing magnetic field, so the induced voltage's direction repeatedly reverses.
- What is the structure of a transformer?
- A primary coil and a secondary coil, both wound around a shared iron core, but not electrically connected.
- Why do transformers only work with alternating current?
- Because a changing magnetic field is needed to induce a voltage in the secondary coil, and only a.c. produces a continuously changing field.
- What distinguishes a step-up transformer from a step-down transformer?
- A step-up transformer has more turns on the secondary than the primary and increases voltage; a step-down transformer has fewer turns on the secondary and decreases voltage.
- State the transformer turns-ratio equation.
- Vp / Vs = Np / Ns
- State the transformer power equation for 100% efficiency.
- Vp × Ip = Vs × Is
- Why are step-up transformers used before transmitting electricity on the National Grid?
- They raise the voltage and lower the current, which reduces energy losses to heating in the transmission cables.
- A transformer has 200 primary turns and 50 secondary turns, with 100 V input. Calculate the output voltage.
- Vs = Vp × (Ns/Np) = 100 × (50/200) = 25 V