# Why field lines are tangent to direction of electric forces

1. Jun 10, 2010

### phoenix0206

can any body tell me why electric field of lines are tangent to direction of electric force

please be fast need it urgently..........

2. Jun 10, 2010

### Stonebridge

They are not "at a tangent". Electric field lines point in the direction of the electric force on a positive charge. They do this by definition.

Do you mean electric potential lines, perhaps?

3. Jun 10, 2010

### Staff: Mentor

It would be better stated the other way around: the electric field (and electric force) at a point is tangent to the field line that passes through that point. We define the field lines so that they have this property.

4. Jun 11, 2010

### Stonebridge

Maybe this diagram will help
The 1st shows the electric field around a single positive charge and the 2nd the field in and around a parallel plate capacitor.
The "field lines" show the direction of the force on a positive charge. The "equipotentials" show places of equal electrical potential.
The field lines are always at right angles to the equipotentials. This is because the field does no work on a charge moving along an equipotential, meaning the force must be at right angles to its direction of motion.

Is this what the OP means?

5. Jun 29, 2010

### AJ Bentley

Why, oh why did someone feel it necessary to invent those dratted imaginary field lines?

No-one talks about 'lines of gravitic force'. In fact people would laugh at you for even raising the concept (I can hear them now...)

6. Jun 29, 2010

### my_wan

Because they make metal shavings look cool :tongue:

7. Jun 29, 2010

### AJ Bentley

Hah! in all the Millenia I've been stuck on this ball of mud I never thought of that!

You're probably absolutely right.