Chapter 26 - 28

Question 1

How can you tell the direction of an electric field from the V vs X graph?

Answer 1

By looking at the slope at a given point.

Question 2

What implies an electric field?

Answer 2

A change in electric potential as the the slope of an electric field depends the change in electric potential over the change in distance.

Question 3

What is the potential in relation to the electric field lines?

Answer 3

The electric field is from high electric potential to low electric potentials.

Question 4

What is the electric potential at the parallel plate capacitors?

Answer 4

The positive plate has high electric potential and the negative plate has low electric potential.

Question 5

What direction is the electric field on an equipotential surface?

Answer 5

The electric field will be perpendicular to the equipotential surface.

Question 6

What is the electric potential of a non-uniform electric field?

Answer 6

The sum of the little bits of E x ds that take place along the path.

Question 7

What can you do to find the electric potential from an electric field?

Answer 7

Find the integral or the area under the curve of an electric field vs distance graph.

Question 8

Does the electric potential depend on a charge?

Answer 8

No, the electric potential is dependent on the electric field but the potential energy can be dependent on a point charge.

Question 9

How can a NET displacement impact the electrons?

Answer 9

With an electric field which will cause the electrons to move in the opposite direction due to the electric force exerted on them and result in a NET displacement.

Question 10

What is drift speed?

Answer 10

The speed at which the sea of electrons flows through the wire.

Question 11

What is an electron current?

Answer 11

The number of electrons that pass through the cross-section of the wire per second.

Question 12

What is the convention current?

Answer 12

The convention is to observe the movement of the positive charge through the wire which moves in the opposite direction to negative charges flowing through the wire which is instead positive end to the negative end unlike electrons which would be negative end to the positive end.

Question 13

What causes the current to flow?

Answer 13

Ohm’s Law explains that V = IR causes the current to flow because the R or resistance is how hard it is to push the current through the wire, where I is the rate of charge flow, and the V is the potential difference across the circuit segment that generates an electric field and pushes the current through.

Question 14

What is the relationship between length, area, and resistance?

Answer 14

To have a larger resistance increase the length of the wire and decrease the area making the current harder to push through. To have a smaller resistance decrease the length of the wire and increase the area making it easier to push through. Also by having a larger area the charges can create more paths and can be pushed easily compared to if the area was small.

Question 15

How is Ohm’s Law related to plumbing?

Answer 15

I = The flow of the water 
V = Water pressure
R = How difficult it can be to allow the water to flow through the pipe

Question 16

What are Electromotive Forces (EMF)?

Answer 16

This is chemical work done per charge to lift the positive charges to the positive terminal.

Question 17

How does electric potential energy change with EMF?

Answer 17

The electric potential energy increases as the work is done to lift the charge to the terminal.

Question 18

What are Kirchoff’s Laws?

Answer 18

1. ) Kirchoff’s Loop Law: If the charge is at the same energy when it gets back to the start of the loop the sum of all of the electric potentials = 0V.
2. ) Kirchoff’s Junction Law: Charges that go in to the system must come out otherwise there will be a large buildup of charge.

Question 19

What is a resistor?

Answer 19

This is any circuit element that dissipates energy such as light bulbs.

Question 20

What is resistance?

Answer 20

The property of dissipating energy by the resistor or how much energy is dissipated which depends on the material of the resistor.

Question 21

What is resistivity?

Answer 21

The resistance of charges in the material to move in response to an electric field.

Question 22

What happens when resistors are in a series?

Answer 22

• Each resistor is on the same wire.
• The voltage is different for each resistor.
• The current is the same.
• The resistance increases and the current is harder to push with more resistors.

Question 23

What happens when resistors are parallel?

Answer 23

• Each resistor is on a different wire.
• The voltage is the same for each resistor.
• The current is different for each resistor.
• The resistance decreases and the current is easier to push with more resistors.

Question 24

How to approach problems with parallel circuits?

Answer 24

Split the circuit and look at it as 2 or more series circuits.

Question 25

What is the potential difference across parallel circuits?

Answer 25

The potential difference across the battery is gained and the potential difference across each resistor in a parallel circuit is lost but it is the same potential difference that is gained across the battery, therefore, it is constant.

Question 26

What is power?

Answer 26

The energy over a time interval as a result of the input from the battery or the output of energy that is dissipated from the resistors.

Question 27

How does the brightness of light bulbs coincide with the number of light bulbs in a series circuit?

Answer 27

In a series circuit, the resistance of the circuit with fewer resistors will be less than the circuit with more resistors therefore the current will be greater in the circuit with fewer resistors I = V/R and R = V/I causing the fewer bulbs to be brighter.

Question 28

How does the brightness of light bulbs coincide with the number of light bulbs in a parallel circuit?

Answer 28

In a parallel circuit since the potential difference across the wire is the same as the battery since the wires have a resistance of 0 and the batteries are the same in both cases the current will be the same as a result the brightness of the bulbs will be the same as well.

Question 29

What are the rules for complicated circuits?

Answer 29

1. ) Look for resistors in a series the current will be the same. 2. ) Look for resistors in parallel the voltage will be the same. 3. ) Find equivalent resistances in steps.

Question 30

What is a capacitor?

Answer 30

Devices that are used for storing charge and energy and deliver that charge and energy quickly.

Question 31

What is capacitance?

Answer 31

The capacity of an object to store charge is the charge per unit of potential difference.

Question 32

How do you charge a capacitor?

Answer 32

To charge a capacitor the battery must do work in order to lift the charge and move it against the electric field that builds up between plates.

Question 33

What happens to the capacitance of capacitors in parallel?

Answer 33

Ceq = Ca + Cb

Question 34

What happens to the capacitance of capacitors in series?

Answer 34

1/Ceq = 1/Ca + 1/Cb

Question 35

What happens to V and Q for parallel capacitors?

Answer 35

The V is constant but the Q changes.

Question 36

What happens to V and Q for series capacitors?

Answer 36

The V changes but the Q stays constant.