Electricity and Magnetism

Online workshop 18 March 2015

Here is your packet of supplies for your upcoming online workshop.
When you join us march 18 please have these materials on hand. Class runs 4:30 to 6:00 PM. We will be online at 4:00 PM to get you connected and running if you haven’t done an online workshop with us before.

Your packet contains:
2 clip leads 
a coil of magnet wire
a sandpaper square
2 Donut magnets
a compass 
a petri dish
dill in a plastic bag
a steel nail, 
a chunk of straw
a rubber band
a PVC tube

You will need to provide:
A little cooking oil
A little aluminum foil
2 alkaline batteries (D-cells are good, but C-cells will work.)
tape any kind will work
wool or newspaper at least 4 inches square (10 cm)

Before class wind the magnet wire around the soda straw chunk, leave two 4 inches long (10cm) leads on each end. Sand the red enamel insulation off at least ½ inch (1cm) of the end of each lead. When you have wound your coil wrap tape around it to prevent it from unwinding.

Wind a coil

To make a battery connector fold aluminum foil into two pads about 1 cm (1/2 inch) wide and 2 cm (1 inch) long and use the rubber band to attach a pad to each terminal of the battery.

battery holder

Put a thin layer of cooking oil in the petri dish. During class you will sprinkle dill onto the oil.

Electric fields

The classic way to find an electric field is by the deflection of a charged object like a piece of Scotch Magic Tape torn off the roll.
When you pull a piece of tape off the roll it becomes positively charged and will deflect in the direction of the electric field when placed in an electric field.
We are not going to do the tape electroscope activities during this workshop but they are great tools for electrostatics so I include them here.

Tape Electroscope long
Tape electroscope short
Electroscope with tape

Electric dill
Electric Dill Snack
Dill, oil, petridish, PVC, wool or newspaper
See electric fields with dill floating on vegetable oil in a petri dish.

An electric field shows you the direction and magnitude of the electric force on a positive unit charge.
When field lines are closer together the field strength is stronger.

Black sand We will not do the black sand activity, but include it because it is a classic.
Black Sand Snack
Magnetic Lines of force snack
Magnet, cardboard,iron filings or black sand
Put a magnet under a piece of stiff cardboard, sprinkle iron filings onto the cardboard, vibrate the cardboard.
The iron filings will line up along the lines of the magnetic field.
By convention we say the lines go from the north pole of the magnet to the south.

Plot field lines
Plot Field Lines PDF
Magnet, paper, compass

A magnetic field shows the direction and magnitude of the magnetic force on a mythical north magnetic monopole.
When magnetic field lines are closer together the magnetic field strength is stronger.

Circles of magnetism

right hand rule single wire 3
Circles of magnetism snack (We'll do a simple version of this snack.)
Battery, Wire clip lead, Compass

Motor effect
Motor effect snack We'll do a newer simpler version of this snack.
battery, wire clip lead, magnet
Hang a loop of wire down over the edge of the table, run current through the wire,
bring a magnet up under the lowest point of the wire and watch the wire deflect.
eight hand rue magnetic force on a current

Wind an insulated wire many times around a steel nail. Attach a battery to the wire momentarily.
When current flows through the coil of wire, the nail becomes an electromagnet. The electromagnet will attract staples and steel paper clips.
You can also simply insert a nail into the soda straw wrapped with wire for the next experiment.
Battery, wire, steel nail, Paper clip or staple

wire, battery, nail, plastic sleeve
Wind a coil of wire around a soda straw. place a nail 1/2 way into the soda straw. Run electric current through the wire coil.
The nail will be attracted into the coil. This is a solenoid. It depends on the divergence, or spreading of the magnetic field beyond the end of the coil.
The field gets weaker with distance, so the nearby magnetic pole of the nail is attracted more than the distant pole is repelled.
right hand rule coil

filed from a solenoid

Electromagnetic Train

World's simplest electric train

Explanation Video by Doug Stith

B field of the battery and magnets
The magnetic field of two magnets with south poles outward attached to a battery.

Scientific Explorations with Paul Doherty

© 2015

17 March 2015