Experiment 1 Simple Electric Motor A simple electric DC moto

Experiment 1: Simple Electric Motor

A simple electric DC motor will help visually demonstrate the relationship between current and magnetic fields. Since a commutator is hard to make with simple materials, this motor will use magnetic force to propel through one half rotation and use only inertia to rotate the other half. When constructed carefully, this simple motor will reach high speeds using only a small alkaline battery!

Materials

Magnet wire
Cylinder magnets
2 Paper clips
9V Alkaline battery
Scissors
Cardboard (from ramp or kit box)

Procedure

Questions

1. In what direction will the magnetic field travel through the nail? Predict this using the right hand rule and the direction of current flow (positive terminal to negative on the battery).

2.From your answer in Question 1, which end will be the north pole of your electromagnet, and which one will be the south? Remember, the direction of the magnetic field is outward from the north pole and inward toward the south pole.

3. Make a sketch of the magnetic field lines for your electromagnet.

4. Bring your electromagnet near the compass to test out its poles. Were your predictions about the north and south poles of the magnet correct?

Bend the 2 paperclips so that they have a round slot for the windings to rest. Tape the paperclips to a steady surface about 5 cm apart, or stick them into a piece of foam board as shown in Figure 5.

Cut a length of wire about 30 cm long. Wrap the wire around a small cylindrical object, such as a C-size battery. Make a coil of 15 turns around the cylinder. Finish the coil by wrapping around opposite sides of the ring to secure everything in place (Figure 6 middle). Leave 4 cm tails coming off both sides to function as an axle that rests on your paperclips.

Hold the coils vertically as if you were standing the circle on end. and rest one axle tail on a flat surface (something that is okay to scratch). Using scissors scrape only one side of the insulation from one tail, and all the insulation from the other (Figure 6 right). The half scraped side will mimic the commutator and brushes on a more complicated motor, only allowing current to flow through the non-insulated side.

4.Connect wires to each of the paperclips. These will be your battery leads.

5.Place a circular magnet on the surface between the two paperclips, as in Figure 7.

6.Suspend the coil by the wire tails across the paperclips so that the windings are directly above the magnet. The windings should spin freely if nudged without wiggling too much. Adjust the tails to make as straight of a line as possible.

7.Connect both leads to a battery (you might want to tape the battery onto the surface, and tape the wires to the terminals). Make sure to leave one wire disconnected to use as a switch.

8.Connect all of the wires to make a circuit, and give the windings a nudge in one direction. The motor should start to spin!

Solution

Fleming\'s Left-Hand Rule
Fleming\'s left hand (motor) rule shows how the current, field, and motion in a motor are related.

You can figure out the direction in which the wire will jump using a handy mnemonic (memory aid) called Fleming\'s Left-Hand Rule (sometimes called the Motor Rule).

Hold out the thumb, first finger, and second finger of your left hand so all three are at right angles. If you point the seCond finger in the direction of the Current (which flows from the positive to the negative terminal of the battery), and the First finger in the direction of the Field (which flows from the North to the South pole of the magnet), your thuMb will show the direction in which the wire Moves.
That\'s...

First finger = Field
SeCond finger = Current
ThuMb = Motion