Electric Fields and Electric Potential
Describing forces, field strength, and electric potential
Electric Fields and Electric Potential
Describing forces, field strength, and electric potential
Physics - Grade 9-12
- 1
A positive test charge is placed near a single positive source charge. Describe the direction of the electric force on the test charge and the direction of the electric field at that location.
Use the rule that like charges repel.
The electric force on the positive test charge points away from the positive source charge. The electric field also points away from the positive source charge because electric field direction is defined as the direction a positive test charge would move. - 2
A negative test charge is placed in an electric field that points to the right. Describe the direction of the electric force on the charge.
The electric force on the negative charge points to the left. A negative charge feels a force opposite the direction of the electric field. - 3
An electric field has magnitude 120 N/C. What is the electric force on a charge of 0.50 C placed in the field?
Use the equation F = qE.
The electric force is 60 N. Using F = qE, F = 0.50 C x 120 N/C = 60 N. - 4
A charge of -2.0 C is placed in an electric field of 15 N/C directed upward. Find the magnitude of the force and state its direction.
The magnitude of the force is 30 N, and the direction is downward. Using F = qE, the magnitude is | -2.0 C | x 15 N/C = 30 N. Because the charge is negative, the force is opposite the field direction. - 5
The electric field strength at a point is 250 N/C. What source charge would produce a force of 500 N on a test charge placed there?
Rearrange F = qE to solve for q.
The test charge would be 2.0 C. Using q = F/E, q = 500 N / 250 N/C = 2.0 C. - 6
Explain the difference between electric force and electric field in one or two complete sentences.
Electric force is the push or pull experienced by a specific charge. Electric field is a property of the space around charges that tells how much force a positive test charge would feel per unit charge. - 7
An electric potential difference of 24 V exists between two points. How much work is done to move a charge of 3.0 C between those points?
Use the relationship between work, charge, and potential difference.
The work done is 72 J. Using W = qV, W = 3.0 C x 24 V = 72 J. - 8
A charge of 2.0 C gains 18 J of electric potential energy when moved to a new location. What is the electric potential difference between the two locations?
The electric potential difference is 9.0 V. Using V = U/q, V = 18 J / 2.0 C = 9.0 V. - 9
State whether electric potential is higher near a positive charge or near a negative charge, assuming each charge is isolated. Give a brief explanation.
Think about the sign of the source charge.
Electric potential is higher near a positive charge and lower near a negative charge. A positive source charge creates positive electric potential, while a negative source charge creates negative electric potential. - 10
A positive charge moves in the same direction as the electric field. Does its electric potential energy increase or decrease? Explain briefly.
Its electric potential energy decreases. A positive charge naturally moves in the direction of the electric field toward lower electric potential. - 11
Two parallel plates create a uniform electric field from left to right. Describe how the electric potential changes as you move from left to right.
Electric field direction shows the direction of decreasing potential.
The electric potential decreases as you move from left to right. Electric field lines point from higher potential to lower potential. - 12
A charge of 4.0 C is moved through a potential difference of 6.0 V. Calculate the change in electric potential energy.
The change in electric potential energy is 24 J. Using U = qV, U = 4.0 C x 6.0 V = 24 J.