If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

# Electric field direction

The direction of an electrical field at a point is the same as the direction of the electrical force acting on a positive test charge at that point. For example, if you place a positive test charge in an electric field and the charge moves to the right, you know the direction of the electric field in that region points to the right. Created by David SantoPietro.

## Want to join the conversation?

• 1) why test charge is*positive* and why not negative ?
2) Do field lines (caused by a single charge) intersect ? // thanks in advance
• 1) This confused me also and as far as I can tell, the reason is simply because of the math which defines the electric field. In the equation E=F/Q, 'E' and 'F' are vector quantities, meaning they have a direction. When 'Q' is a POSITIVE number (as it is when you have a POSITIVELY charged particle), the direction of the electric field is the same as the direction of the force experienced by the particle. If instead you decide to use a NEGATIVELY charged test particle, the charge on the particle will be a NEGATIVE number. So if we go back to the equation for our electric field E=F/Q, 'Q' will be a negative number. Since 'F' is a vector quantity, dividing it by a NEGATIVE number will change its direction, meaning that now, the direction of the force experienced by the particle will be opposite from the direction of the electric field. So provided we stick to our example of a POSITIVELY charged particle creating the electric field, this model satisfies what we actually observe, which is two positively charged particles repelling each other, and a positively charged particle attracting a negatively charged particle. Hope that helps!
2) Field lines caused by a single charge do not intersect as this would mean that a test particle present at this point of intersection would experience two forces in different directions. We know that this does not happen.
• why do fields caused by +ve charges radially outwards and not inwards?
• The direction of the fields is defined by the force on a positive test charge. A positive test charge is repelled by a positive charge so the direction is away.
• So instead of two positive charges repelling what if there was two negative charges repelling, would the electric field be pointing inwards or outwards? And which direction will the electric force be between the two negative charges?
• The electric field created due to the negative charge is radially inwards. But as there is another negative charge, due to E=F/Q(here Q is negative thus) feels a force in the direction radially away from the first negative charge. Thus Field would be towards the negative charge and force is opposite to the direction of this field.
• If the negative charges have a eletric field wich points radially inwards
why do two negative charges not attract each other?
or the eletric field doens't points to where they exert force?
I think I'm looking at it from a wrong viewpoint, then if someone could clear the things up to me, I'd be very grateful
• hi Marcus,
The same way that positive charges would push each other, negative charges, by this analogy, would pull away from one another as their fields would point radially inwards
(1 vote)
• Why electric field lines don't intersect at all ?
(1 vote)
• they can't intersect because they are defined by the the direction of the force they would apply to a charge placed in a particular location. If they crossed, it would mean that the force points in two directions, and that's not possible.
• What about the direction od the electric field of a negative charge wheh a negative test charge comes around, outward direction right?
• Is the direction of the electric force in the same direction with the electric field?
• The force a field applies to a charge depends on the sign of the charge.
The direction of the field is DEFINED by the direction of the force it would put on a positive charge. So that tells you that the force on a positive charge will be in the same direction as the field, but the force on a negative charge will be in the opposite direction.
• if you just have two magnets and they are pushing away from each other can you determine whether their charges are negative or positive?
(1 vote)
• magnets don't have positive and negative charge, they have North and South.
You can't tell which pole is which without a known reference pole.
The most easily accessible known reference pole is the one we call "Magnetic north", the direction a compass points. A permanent magnet's NORTH pole is attracted that direction.
• It seems like the electric field in this lecture is 2 dimensional (probably for the purposes of display & to simplify teaching). Is it not a 3 dimensional phenomenon occurring in & out of the screen as well- like a sea urchin's spines?
• "(probably for the purposes of display & to simplify teaching)"

Yes! And you are also correct in thinking that the electric field is a 3 dimensional phenomenon - they are coming in and out of the screen. :)
(1 vote)
• What is it with those fancy curved lined electric fields? Why are some field lines curved?