Electricity and Magnetism

Question 1

Define electrical power

Answer 1

Electrical power is the rate at which electrical energy is generated or transformed.

Question 2

What is electrical power measured in?

Answer 2

Electrical energy is measured in kilowatt hours (kWh 10^3) for homes or megawatt hours (MWh 10^6) for power plants.

Question 3

How many joules is 1 kilowatt hour equal to?

Answer 3

3.6x10^6 Joules

Question 4

Define electrical potential

Answer 4

Electrical potential is the amount of energy needed to move a quantity of electrons closer to one another. The electrical potential difference is measured in volts.

Question 5

What is a voltmeter and how must it be connected?

Answer 5

A voltmeter is a device used to measure potential difference. It must be connected in parallel to create separate paths for a small amount of electrons to flow.

Question 6

Define direct current

Answer 6

Direct Current (DC) is the flow of electrons in one direction, through a circuit. In other words, the rate of charge flow.

Question 7

How much electrons is 1 coulomb of charge?

Answer 7

1 coulomb of charge is equal to 6.2x10^18 electrons.

Question 8

What is an ammeter and how must it be connected?

Answer 8

Electric current is measured using an ammeter. They must be connected in series so all the electrons flow through to give an accurate reading.

Question 9

Define electrical resistance

Answer 9

Electrical resistance (R) is the property of matter that describes how difficult it is for electric current to flow through a circuit.

Question 10

Define resistor

Answer 10

A resistor is an electrical device that has a specific resistance.

Question 11

What is Ohm’s Law?

Answer 11

The potential difference between any 2 points in a conductor varies directly with the current between the points. Potential difference and current are directly proportionally to each other.

Question 12

What does the slope on a V/I graph represent?

Answer 12

The slope on a V/I graph represents the resistance of a circuit.

Question 13

Define field

Answer 13

A field is a region of space surrounding an object that can cause another object to experience a force.

Question 14

Define magnetic field

Answer 14

A magnetic field is a 3-D region of space, surrounding a magnet that will exert a force on magnetic objects.

Question 15

What are the 4 things that one must remember when drawing magnetic field lines?

Answer 15

Magnetic field lines are more intense (concentrated) at the poles, they are drawn from N-S externally and S-N internally, they never cross, and they are drawn closer together where the magnetic field is stronger.

Question 16

What is convectional current?

Answer 16

Conventional current goes from the positive to the negative terminal.

Question 17

What is Oersted’s principal?

Answer 17

Oersted’s principal states that whenever a charge moves through a straight conductor, a circular magnetic field is produced around the conductor.

Question 18

What is the motor principal?

Answer 18

The motor principal states when a current carrying conductor (wire) cuts through an external magnetic field (bar magnet), the conductor experiences a magnetic force perpendicular to the current flow and the external magnetic field.

Question 19

Define electromagnetic induction

Answer 19

A changing/moving magnetic field is required to produce an electric current around a conductor.

Question 20

What are factors that affect induction?

Answer 20

The factors that affect induction are if a conductor is coiled, the number of loops and the faster the magnetic field moves.

Question 21

What is Lenz’s Law?

Answer 21

Lenz’s law states that if a changing magnetic field induces a current in a coil, the direction of the induced current is such that it’s magnetic field opposes the motion of the existing magnetic field.

Question 22

What is a transformer?

Answer 22

A transformer is a device used to raise or lower AC voltage.

Question 23

How much V of power comes into a standard home?

Answer 23

120 V

Question 24

What is a step-up transformer?

Answer 24

A transformer that has more secondary windings than primary windings.

Question 25

What is a step-down transformer?

Answer 25

A transformer that has less secondary windings than primary windings.

Question 26

How is voltage and current related?

Answer 26

Voltage is inversly proportional to current.

Question 27

How is voltage and the number of windings related?

Answer 27

The voltage is directly proportional to the number of windings.

Question 28

How is current and the number of windings related?

Answer 28

The current is inversely proportional to the number of windings.

Question 29

How should you set up transformer problems?

Answer 29

One must always set up the ratios with the unknown on top.

Question 30

Why is transmission important?

Answer 30

Transmission of AC electricity requires the use of transformers to minimize energy lose.

Question 31

What are step-up transformers used for?

Answer 31

Step-up transformers at the generating station are used to increase voltage and reduce current for transmission. The less current results in less traffic on the power lines and less energy that is lost due to friction.

Question 32

What are step-down transformers used for?

Answer 32

Step-down transformers are used throughout the grid to bring voltages down to levels that can be used in homes.