Materials

Water tank, Tektronix CFG250 function generator, Fluke 73 multimeter, cables, copper conductors tap water.

Theory

Michael Faraday hypothesized that an electric field exists in the space which surrounds any set of charged conductors. By connecting a pair of conductors to a battery, one conductor becomes positively charged and the other becomes negative. As a result we establish a voltage difference between them. We arbitrarily use the convention of defining the negative conductor to be at zero volts. This is called ground, or “grounded”.

The grounded conductor forms an equipotential surface of zero volts. This means that every point on the conductor is at the same energy. The positive conductor also forms an equipotential surface, but at a higher voltage. Therefore, in the space between the two conductors the voltage must change continuously as one moves from the negative conductor to the positive conductor. Between the two conductors lie surfaces of equal potential, or equipotential surfaces. In principle there are in infinite number of equipotential surfaces in the space surrounding the two conductors.

Once the equipotential surfaces have been mapped, it becomes an   easy task to draw the electric field lines which connect the two conductors, the following rules must be adhered to:

Field lines always start on positive charges and terminate on negative charges, with arrows indicating the direction.

Field lines always meet the conductor perpendicular to the conductor’s surface

Field lines always cross equipotential surfaces at right angles.

Field lines tend to spread out radially to fill the available space.

Equipotential Lines for Parallel Conducting Plates Field lines (black) are perpendicular to the plates Equipotential lines (red) are parallel to the plates.	Equipotential Lines for a Point Charge Electric field lines (black) radiate outward Equipotential lines form red circles around the charge

Procedure 

Check with your me before you turn on the signal generator! 

Lab Analysis

ð Your lab should include 2 completed maps which show the conductors, the spacing, the equipotential lines and the electric field lines.

         Draw these in different colors or solid and dashed and clearly indicate the scheme used. Include the readings recorded for each field line and each equipotential line.

ð Answer the following questions, clearly labeled, in your report.

       Ø  Is work required to move a charge along an equipotential surface?

       Ø  Is work required to move a charge along an electric field line?

       Ø  Why is the electric field essentially constant between the two plates?

       Ø  Why do field lines never cross?

Format

ð Regular format required for all actual labs.

ð Include the above requirements in the appropriate paragraphs of the prescribed format.

ð Attach a copy of these instructions to your lab report.

ð As usual, obtain my initials on your well-organized data sheet before leaving the lab and submit that along

       with your report.

NOTES

note 1: Top row of buttons, 4th button from left, in position.

note 2: Second row of buttons, Volts, out position. p-p means point to point.

note 3: Top row of buttons, last button on right, in position.

note 4: Fill the tray with about 1 cm of water.

note 5: Record the readings in your report