Electric Fields U4

Question 0

Why are field lines pointing away from a positively charged particle

Answer 0

Because these lines show the direction a test positive charge would move

Question 1

Define an electric field

Answer 1

Force acting per init charge

Question 2

Uniform field : E=

Answer 2

V/d

F/Q

Question 3

If you double the distance between two plates in a uniform field what happens to the V? Why?

Answer 3

The v=1/2 because of E=V/d ,

They’re inversely proportional

Question 4

What happens to E when you increase the potential difference between two plates in a uniform field

Answer 4

E increases

Question 5

What direction do you draw any electric field lines

Answer 5

Away from a positive charge

Towards a negative charge

Question 6

Why does the E field for a radial field get weaker as you get further away from the charged particle?

Answer 6

Because the field lines are further apart as you move further away from the charged particle therefore the E field is weaker

Question 7

What is the surface area of a sphere

Answer 7

4(pi)r^2

Question 8

If you double the radius of a sphere what happens to the surface area? What is this called?

Answer 8

4X larger

Inverse square law

Question 9

What is E proportional to for a radial field?

Answer 9

1/r^2

Q/r^2

Question 10

If E is proportional to Q/r^2 then what does E equal?

Answer 10

E=k(Q/r^2)

Where k is a given constant

Question 11

When does Coulomb’s law apply?

Answer 11

When there are two charged particles in an electric field

Question 12

If the force Squire’s from Coulomb’s law is negative what does this mean?

Answer 12

It’s an attractive force because the charges are opposite

Question 13

E=? (Coulomb’s law) and therefore derive F

Answer 13

F=EQ2
KQ1/r^2=F/Q2
KQ1Q2/r^2=F

Question 14

The Coulomb’s law equation is

Answer 14

F = k Q1Q2/r^2

Question 15

What is the proportion of forces on two charged particles in an electrical field

Answer 15

They are equal and opposite

Question 16

What’re the units of electric field strength

Answer 16

N/C

Question 17

What is the field if the field strength is the same everywhere?

Answer 17

A uniform field

Question 18

What is E inversely proportional to in a radial field

Answer 18

r^2

Question 19

What is an experiment to investigate a uniform field?

Answer 19

The oil drop experiment

Question 20

Describe the oil drop experiment when the circuit is off/on; and what happens when changing the distance and potential difference in the circuit?

Answer 20

1) an atomiser creates a fine mist of oil drops that are charged by friction as they leave the atomiser
2) when the circuit is off the drops fall from the top to the bottom plate due to their weight
3) when the circuit is switched on, the potential difference between the two plates creates a uniform electric field, which exerts a force on the oil drops.

A negatively charged oil drop can be made to float between the two plates by balancing the upward force from the electric field and the downward force of the oil drops weight.

4) if you increase the potential difference the electric field strength will increase and the oil drop will wove towards the positive plate
5) if you increase the distance between the two plates or decrease the potential difference then the field strength is reduced therefore the oil drop will fall to the bottom plate due to it’s weight being a larger force.