Unit 8: Electricity

The force between two charge q1 and q2 is F when separated by a distance r. What is the force between two charges 3q1 and 4q2 when separated by a distance 2r?

3F

Series Circuits

All devices are connected in a continuous loop; if one device fails, all devices fail

What happens to the charges as they move in the external and internal circuit?

As a charge moves in the external circuit, it loses electric potential energy. As a charge moves in their internal circuit, it gains electric potential energy.

Which of the following will cause the current through a circuit to decrease? (Think Delta V = IR)

Decreases the potential difference and increase the resistance

Parallel Circuits

Devices are connected via individual branches (loops), so changes flow through different pathways to reach devices; if one device fails, the other devices will continue to work.

Electric Field Strength

Electric field strength is a measure of the force per 1 Coulomb of charge exerted on a test charge at a given location in an electric field. This is a vector quantity. A test charge is used to measure the strength of an elecrtic field produced by a source charge. The magnitiude of the electic field strength is dependent upon the quantity of chaarge on the source charge and the distance of seperation from the source charge. The direction of the electric field vector is the direction that a positive test charge is pushed or pulled when in the presence of the electric field

Electric Force

Fc = kq1q2/r^2(Coulomb's law): Fc includes attractive and repulsive interactions between two charges

Gravitational Force

Fg = Gm1m2/r^2(newton's law of universal gravitation): Fg includes attractive interactions only between two objects with mass

Halving the distance (decreasing by a factor of two) between two charged objects will cause the electrical force between them to be __ the initial force

Four times 1/2r -> 1 / (1/1/4) -> 4

Describe the properties of good conductor and good insulator

Good conductors are materials with many free electrons through which charge can easily flow. (Ex. Metals, human body, salt solution) Good insulators are materials with few free electrons through which charges canno easily flow. (Ex. Plastics, rubber, non-metals)

What would cause the electrical force between two objects to increase? (Fc = kq1q2/r^2)

Increase the charge on one object, increse the charge on both objects, decrease the distance between the objects' centers

Electric field strength

The electric field carries/produces an electric field. Variable: E Unit: N/C

A positive charges moves within a uniform electric field. The charge moves in the opposite direction of the field lines.

The electric field does negative work on the charge. The potential difference across the points is positive. The charge gains electrostatic potential energy. The charge moved to a location of higher electric potential.

A positive charge moves within a uniform electric field. The charge moves in the direction of the field lines.

The electric field does positive work on the charge. The potential differnce across the points is negative. The charge loses electrostatic potential energy. The charge moved to a location of lower electric potential.

What does the electric force between two objects depend on? (Fc = kq1q2/r^2)

The electric force between two objeccts depends on the charge on the objects and the distnace between the objects.

Describe the quantization requirement of net charge. Is it possible for a particle to have a net charge of 4.3e? Of 5.6 x 10^-19 C?

The net charge muse be an integer multipl eof the elementary charge, e. It is not possible for 4.3e to be a net charge because it is not an integer multiple. It is not possible for 5.6 x 10^-19 C to be a net charge beacuse 5.6 x 10^-19 C/1.6 x 10^-19C is 3.5, which isnt an integer multiple

In order for electric current to flow through a circuit, which must be true about the shape of the circuit

The wire must be connected to a battery and a device(s) in a continuous loop.

Potential Difference

The work done on a small positive charge as it moves from A to B. Variable: delta V Unit: V

Electric force/Coulomb force

Variable: Fc Unit: N

Electrostatic potential energy

Variable: PE Unit: J

Electric potential

Variable: V Unit: Volts

Work

Variable: W Unit: J

Electric Charge

Variable: q Unit: Couombs (C)

As more and more resistors are added in parallel to a circuit, the equivalent resistance of the circuit __ and the total current of the curcuit __.

decreases, increases

What is the elementary charge?

e = 1.6 x 10^-19 C This is the electric charge carried by a single proton or electron.

Two neutral objects A and B are rubbed together. During the process, object A becomes charged positively and object B become charged negatively. This is because __.

electrons are transferred from object A to object B

Doubling the distance between two charged objects will cause the electrical force between them to be __ the initial force

one fourth 2r -> 1/(2)^2 -> 1/4Fc

In general, electric field lines shows the direction of the force on a ___.

positive test charge placed near a source charge

According to Ohm's Law, how is the current related to the resistance and voltage off circuit?

Current and resistance are inversely proportional Current and voltage are directly proportional

Potential difference

Measure how much electric potential energy charges lose as they move between 2 points on a circuit. Also called voltage. Variable: Delta V Unit: V

Resistance

Measures how difficult it is for charges to flow through a particular electrical device Variable: R Unit: ohms

Current

Measures rate that a quantity of charge is flowing through a device Variable: I Unit: A

Inside a batter, charges move from the __ to the __.

Negative terminal, positive terminal

Describe the behaviors of electrical attraction and repulsion between charges particles

Positive and negative charges are attracted to one another. Two positive charges or two negative charges repel one another.

Outside of a battery, charges moves from the __ to the __

Positive terminal, negative terminal

What are the two types of charge? Which subatomic particles carry charge?

Protons(+e): carry positive charge Electrons(-e): carry negative charge