Field Intensity and Distance
How electric-field strength changes with distance from a charge
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Teachers - Need to use your overhead? Field Intensity
Show Me The Physics
Charging Pith balls. Explain this.
St. Mary's University | Onsite |
Review Name these charges
A is negative B is positive
Fill in the Blank Notes
H) Field Intensity and
Distance
1) Spherical point charge
Field intensity varies
Inverse Square Law Animation Double distance from spherical charge, the field intensity ....
is quartered
2. Charged Rod - the field intensity varies inversely with distance
If the distance to the rod is
reduced to 1/3 its original distance,
would be 3 times greater
Electric Field Strength and Distance
Show Me The Physics Website
Review - Can you explain this?
Review - Name these charges
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Check Your Understanding
5 quick questions — pick an answer to see if you’re right.
1. For a spherical point charge, how does field intensity vary with distance?
2. You move twice as far from a spherical point charge. The field intensity is
3. The field is 36 N/C at some distance from a point charge. What is it at three times that distance?
4. For a long charged rod, the distance to the rod is reduced to ⅓. What happens to the field intensity?
5. A student says doubling your distance from a long charged rod makes the field ¼ as strong. What is correct?
Field Strength Near a Charged Sphere
Students used a field sensor to measure the electric field strength at different distances from the center of a small charged sphere. The data are shown in Table 1.
Table 1: Field Strength vs. Distance
| Distance (m) | 0.10 | 0.20 | 0.30 |
|---|---|---|---|
| Field Strength (N/C) | 3600 | 900 | 400 |
Which relationship do the data show?
▶ Want a challenge? Open 6 more Regents-style questions (harder · mixed formats)
Challenge score: 0 / 6
C1. Using the data point at 0.10 m, substitute numerical values into a mathematical representation that can be used to determine the charge on the sphere. Then calculate the charge.
C2. Predict the field strength at 0.40 m.
C3. At what distance from the center of the sphere would the field strength be 1600 N/C?
C4. A student makes the following claim.
Place a check mark in either the Support or Refute box. Justify your response using a mathematical relationship.
C5. Which quantity stays constant for all three data points?
C6. Describe how the students could graph their data so that the points fall on a straight line. Identify the quantities on each axis, and explain what the slope of the line represents.