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A hand-cranked demonstration generator has a coil of 250 turns, each of area 60 cm², in a field of…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A hand-cranked demonstration generator has a coil of turns, each of area , in a field of T. The handle turns the coil times each minute. Find the frequency of the emf, and its peak value.
Need a reminder? The key ideaShow
A coil of turns and area turning at angular speed in a field has , with the peak emf and . The mechanical power that turns it equals the electrical power, . The average power in a resistor is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. , , T, and turns each minute.
Plan. Find , then , then .
Step 1. The frequency. . The emf also takes s for each cycle.
Step 2. The angular speed. .
Step 3. The peak emf. .
Answer: Hz, and a peak emf of V.
Check. A small coil in a weak field gives about a volt, which is enough to light a torch bulb a little.
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