Field lines indicate the direction of the force experienced by a small positive test charge and the size of the force.
Key Concepts
The electric field between two parallel plates is uniform, which means that the size of the electric force is the same everywhere.
To draw a uniform field:
- Use a ruler at all times - every field line is straight and parallel
- The field lines should have equal distances between them
- The field lines should be perpendicular to the plates
- The direction of force is from the more positive plate to the less positive plate
NB: An electric force is experienced by charges where there is any field.
An electric field is a region of space where a charge will experience a force.
We can't see fields, but we can draw field lines to give a visual representation. These show the direction a positive charge would accelerate.
When drawing field lines:
- Make sure they start on a + and/or end on a -
- Ensure your lines never cross (NB: force is a vector quantity so there would be a resultant direction)
- Lines drawn closer together indicate that the field is stronger. The field lines drawn from a point charge should be evenly distributed.
- Straight lines need to be drawn with a ruler
- Use arrows to show the direction of the lines
Use quizzes to practise application of theory.
START QUIZ!
The diagram represents a charge surrounded by 4 test charges, the arrows represent the force experienced.
Which charge has the wrong arrow
B should be shorter than A
Two charges are arranged as shown.
If the mass of the small charge is very much less than the big one its velocity will
It will always have a force to the left so will always accelerate but the acceleration will get less as it gets further away.
3 charges are arranged as shown.
What will happen if the are free to move
Two charged balls are arranged on strings as shown.
When released the balls will
The oscillation is not SHM as the force is not proportional to displacement
A small charge is projected into the electric field shown.
The path of the particle could be
B is a parabola, C is part of a circle
A small charge is projected towards a large one as shown
Which point represents a position that the charge could be in a short time later
The small charge will experience a force away from the big charge
The small positive charge is released at the point shown
Which line gives the correct motion of the particle
Initial motion is in the direction of the field but the acceleration is in the direction of field but not velocity.
How much of Electric field lines have you understood?
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