# Planning Lab to measure how emf varies with an angle

• rock.freak667
In summary, the conversation discusses designing an experiment to investigate the relationship between induced e.m.f. and angle of rotation in a metal disc placed in a uniform magnetic field. The experiment would involve keeping the variables of E and \theta constant, using a motor to rotate the disc at a constant speed, and using a large solenoid to keep the magnetic field constant over the entire surface area of the disc. The angle would be measured by tipping the magnet at a known fixed angle using a protractor.
rock.freak667
Homework Helper
A metal disc is placed in a uniform magnetic field of flux density,B,acting through the plane of the disc at and angle,$\theta$.When the dis is rotated an e.m.f. is induced between the centre and the rim of the disc.

http://img158.imageshack.us/my.php?image=scanlc2.jpg

Design an experiment to investigate how the induced e.m.f.,E, depends upon $\theta$

ok, since I am I need to measure E and $\theta$, I need to keep the rest constant.
$\omega$ would be kept constant by using a motor with a constant power output to rotate the disc.

To keep B constant, use a solenoid and the field should be uniform through the centre of it. (Not sure about that)
But I do not know how to go about measuring the angle.$\theta$

"To keep B constant, use a solenoid and the field should be uniform through the centre of it. (Not sure about that)"

You would need a very large solenoid since you want B to be constant over the whole surface area of the disk. i.e A large pole-face.

"But I do not know how to go about measuring the angle..."

Just tip the magnet at a know fixed angle relative to the disk surface. Your choice.

Last edited:
dlgoff said:
"
Just tip the magnet at a know fixed angle relative to the disk surface.

So take a protractor and just move the magnet relative to the protractor?

## 1. What is the objective of the lab?

The objective of the lab is to measure how electromagnetic force (emf) varies with different angles. This will help us understand the relationship between emf and angle and how it affects the strength of the electromagnetic field.

## 2. What materials and equipment are needed for the lab?

The materials and equipment needed for the lab include a compass, wire, a battery, a resistor, a voltmeter, and a protractor. Optional materials include a multimeter and a graphing calculator.

## 3. How do I set up the lab?

To set up the lab, first, connect the wire to the positive terminal of the battery. Then, connect the resistor to the other end of the wire. Next, connect the voltmeter to the resistor. Finally, place the compass near the wire and use the protractor to measure the angle between the wire and the compass needle.

## 4. How do I collect data during the lab?

To collect data, start by setting the compass at a specific angle (e.g. 0 degrees) and record the voltage reading on the voltmeter. Then, increase the angle by a set amount (e.g. 10 degrees) and record the voltage reading again. Repeat this process until you have collected enough data points to create a graph.

## 5. How do I analyze the data and draw conclusions?

To analyze the data, plot the voltage readings on the y-axis and the corresponding angles on the x-axis. Then, analyze the trend of the data points on the graph and draw conclusions about how emf varies with angle. You can also use mathematical equations, such as Ohm's law, to further analyze the relationship between emf and angle.

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