Question

how can I determine the direction of electric force and the electric field? are negative charges always opposite in direction?

Answer 1

The direction of electric field depends on the nature of charge. If we have positive test charge , then the electric field lines will move towards the charge and if we have a negative test charge, then the electric field lines will move away from the charge.

Direction of electric force can be determined using the fundamentals of charge interactions.

Suppose we have two negative chages kept in line then force on each charge from other charge will be opposite to each other means they will repel each other.

In case of one negative and one positive charge kept in line, force will be attractive .

Here is the a simple diagram showing all possible cases.