Question

5. Drag a negative charge onto the grid and use the tape measure to place this charge 0.5 m directly to the right of the positive charge.

6. Drag a Voltmeter back onto the grid. Use the tape measure and the sensor to measure the electric potential at a distance of 0.5 m directly above the negative charge. Record below.

V=___5.760V______          

1. Use what we’ve learned in class to calculate the electric potential at this location. Show all work below. ( 1nC = 1 x 10^-9 C)

2. Does this agree (reasonably) with your measured value? If not you might need to check something.

3. Use the voltmeter to plot the equipotential surfaces that correspond with 4 V and -4 V. Sketch the charges and equipotential surfaces below.

4. What is the angle between the electric field and the equipotential surface?

5. Explain why the angle between the equipotential surfaces and the electric field is ALWAYS the angle you observed in question d.

How much work is required to bring a 3 uC charge from a point on the -4 V equipotential surface to a point on the 4 V equipotential surface? Show all work.

Answer 1

(a)

If we go by the theory

V = kq / r

V = 9e9 * 1e-9 / 0.707 - 9e9 * 1e-9 / 0.5

V = 12.72 - 18

V = 5.27 Volts

_____________________________

(b)

yes, the value is reasonably okay with an error of 9.3 %

_________________

(c)

do it yourself

________________

(d)

angle between electric field lines and equipotential lines is always 90 degree

________________

(e)

Because when the potential becomes constant, the negative potential gradient also becomes zero, so electric field has to be normal to this surface

______________-

(f)

W = qV

W = 2.4e-5 J