A line of force is defined as what?

• A. A line representing the flow of current in a conductor
• B. A line indicating the rate of energy transfer
• C. A line in an electric or magnetic field that shows the direction of the force
• D. A path of least resistance in a circuit

Answer: (C)

Lines of force visualize the direction a force would act on a test charge in a field. In an electric field, a small positive test charge would experience a force along the tangent to the line at every point, so the line shows the direction of the force. The lines also illustrate field strength by density: closer lines mean a stronger field. In magnetic fields, the lines indicate the direction of the magnetic flux, shaping the field’s geometry even though the actual magnetic force on a moving charge follows q(v × B). So a line in an electric or magnetic field that shows the direction of the force captures the intended meaning. The other ideas—flow of current, rate of energy transfer, or a path of least resistance—describe different concepts and don’t define lines of force.