Question

Please answer A through D

Work done can also be determined by considering movement across equipotentials. This can be written as: Vn is the electric potential at point P This tells us that the work done by you is dependent only on the magnitude and type (+ or -) of the electric charge you are trying to move, and the difference in electric potential from the ending point to the starting point. Both of these equations could yield positive or negative values for work. Positive work for you means that you (or some outside influence) are doing work against the field to move the charge. Negative work for you means that you aren't doing any work and the particle moves the way the field would naturally push or pull the charge. 3) Use the equations above that determines work and your sketches (for electric fields and equipotentials) to state if each of the situations below would be + or - work: a) Moving a + charge from a point of higher electric potential to one of lower electric potential. Explain your reasoning for this first case b) Moving a - charge from a point of higher electric potential to one of lower electric potential. c) Moving a + charge from a point of lower electric potential to one of higher electric potential. d) Moving a - charge from a point of lower electric potential to one of higher electric potential.

Answer 1

3 (a)

we know electric field lines travel from higher potential to lower potential and a positive charge experience force in the same direction as the electric field . hence the force on a positive charge in electric field from high potential to low potential is in the same direction as electric field. So no work is required from us to move the charge.

so work done is negative

(b)

we know electric field lines travel from higher potential to lower potential and a negative charge experience force in the opposite direction as the electric field . hence the force on a negative charge in electric field from high potential to low potential is in the opposite direction as electric field. So work is required from us to move the charge in the direction of electric field from high to low potential

so work done is positive.

(c)

we know electric field lines travel from higher potential to lower potential and a positive charge experience force in the same direction as the electric field . hence the force on a positive charge in electric field from high potential to low potential is in the same direction as electric field. So work is required from us to move the charge in opposite direction of the electric field.

so work done is positive

(d)

we know electric field lines travel from higher potential to lower potential and a negative charge experience force in the opposite direction as the electric field . hence the force on a negative charge in electric field from high potential to low potential is in the opposite direction as electric field. So no work is required from us to move the charge in the direction opposite of electric field from low to high potential.

so work done is negative