4.7 Potential Gradient and Electric Potential

Question 1

What is the electric potential?

Answer 1

• the energy a charged object posses
• by virtue of its position within an electric field
• per unit charge

Question 2

what does electric field strength tell us (relating back to potential)

Answer 2

how quickly the electric potential is changing (the stronger it is the greater the change)

Question 3

What is potential gradient? in this topic?

Answer 3

rate of change of electric potential

Question 4

What is the equation for electric potential in a uniform electric field? What is each symbol?

Answer 4

e = -v/d 
e = electric field strength 
v = change in pd (difference in potential between 2 points) 
d = r of 2 charged points (plate to a charge when working with electric potential)

Question 5

Why is v negative in this equation?

Answer 5

Since the direction of the electric field is opposite to the direction of increasing pd between the 2 plates.

Question 6

Why is v the same as energy in this equation?

Answer 6

As V = Jc^-1 in units, as electric potential is per 1c, it must be the same as 1J when multiplied by 1C

Question 7

As a charged object moves towards the ‘exit’ of electric field what does the energy change into as v decrease? this mostly applies to radial fields

Answer 7

kinetic energy (speed of charged object)

Question 8

What would be the d in the e = -v/d equation.

Answer 8

Distance from negative plate (no potential difference)

Question 9

Is electric potential a gradient or a scalar?

Answer 9

vector, it can be both negative and positive in radial fields depending upon point charge

Question 10

Where is electric potential greatest in a uniform field?

Answer 10

At positive plate

Question 11

Equation for potential gradient with a positive point charge creating a radial electric field? What does each symbol represent? (assuming thing put into electric field is positive) - repulsive

Answer 11

v = q / 4(pi)EoR 
v = electric potential 
q = charge (of thing creating field) 
Eo = constant 
r = distance to thing creating field

Question 12

Equation for potential gradient with a negative point charge creating a radial electric field? What does each symbol represent? (assuming thing put into electric field is positive) -

Answer 12

v  = - q/4(pi)Eor  
v = electric potential  
q = charge 
Eo = constant 
r = distance

Question 13

Of what is r and q in equations for electric potential of radial fields.

Answer 13

Of thing creating electric field

Question 14

What are electric potential values when relationship between point charge and charge placed into electric field.

Answer 14

For repulsive force between point charge and charged object it is positive
For attractive it is negative

Question 15

What is the relationship between v and r?

Answer 15

inversely proportional v = 1/r

Question 16

What is the value of constant Eo?

Answer 16

8.85 x 10^-12

Question 17

When starting from r = 0 to point charge how does magnitude of V change as we get further away when the force between point charge and charge is repulsive. What is the initial value of V?

Answer 17

For repulsive it decreases , it starts high

Question 18

In a radial field with repulsive force between charge and point charge where is V greatest?

Answer 18

Closest to point charge

Question 19

When starting from r = 0 to point charge how does magnitude of V change as we get further away when the force between point charge and charge is attractive? What is the initial value of V?

Answer 19

it increases, it starts negative low

Question 20

How can we find the potential gradient in an E/r graph?

Answer 20

Area between 2 points

Question 21

How can we find the electric potential in E/r graph?

Answer 21

Pick one point and multiply e by r.

Question 22

What happens as a charge is placed and moved away within an electric field of an oppositely charged point charge? what does it gain

Answer 22

it is repelled and gains kinetic energy

Question 23

What happens as a charge is placed and moved away within an electric field of a point charge of the same charge? what does it lose

Answer 23

It wants to be attracted, so it loses Ek as it gets further away