13: Efield

Question 1

Define Coloumb’s Law

Answer 1

Coloumb’s Law states that the magnitude of the electric force between two point charges is proportional to the product of their charges and inversely proportional to their square of their separation

Question 2

Define Efield

Answer 2

Efield is a region of space in which a charged particle experiences an electrical force

Question 3

Define electrical field strength

Answer 3

Electrical field strength is the electrical force per unit charge acting on a small stationary test charge placed at that point.

Question 4

How are EFS and Eforce related in terms of direction?

Answer 4

EFS always points from higher potential to lower potential

If charge is positive (+): Eforce is in the same direction as EFS
If charge is negative (-): Eforce is in the opposite direction as EFS

Question 5

Define EPE

Answer 5

EPE of a charge at a point in a efield is the work done by external agent to bring a small test charge from infinity to that point without any change in kinetic energy

Question 6

Define Electric Potential

Answer 6

EP of a charge in a point in a efield refers to the work done per unit charge by an external agent in bringing a small test charge from infinity to that point without any change in KE

Question 7

Direction of EP and EPE

Answer 7

Direction of EP is always from higher potential to lower potential

EPE depends on the charge
if same charge move towards same charge, there is EPE gain
if same charge move away from same charge, there is EPE loss

if different charge move away from different charge, there is EPE loss
if different charge move towards different charge, there is EPE gained

Question 8

How to find force when given equipotential sketch?

Answer 8

1. Must check if question say scallable
2. Use ruler to measure a higher and lower potential
3. use formula E = Difference in potential / distance
4. F = qE

Question 9

What condition must standard electrolytes have?

Answer 9

Must be multiple of elementary charge 1.6x10^-19

Question 10

Why is gravitational force not considered when dealing with alpha/electrons?

Answer 10

MUST SAY: Mass is very small, thus gforce is small and insignificant AS COMPARED TO electrical force

Question 11

1. Imagine <E-r> and <V-r> graph of ++:
   Imagine <E-r> and <V-r> graph of +-:</V-r></E-r></V-r></E-r>

Answer 11

1. <E-r> From positive to negative, point where E = 0 is at equilibrium point
   </E-r>

<V-r> Negative throughout, point at r for E=0 has gradient=0

2. <E-r> Positive throughout, there no equilibrium point
<V-r> From positive to negative, where V=0, EPE=0
</V-r></E-r></V-r>