5. Electricity and Magnetism

Question 1

Law of Conservation of Charge

Answer 1

the total electric charge of an isolated system remains constant

Question 2

Conductor

Answer 2

material through with electric charge flows freely

Question 3

Insulator

Answer 3

material through which electric charge does not flow freely

Question 4

Coulomb’s Law

Answer 4

The electric force between two point charges is directly proportional to the product of the two charges and inversely proportional to square of the distance between them, and directed along the line joining the two charges. (F = k q1 q2 / r2)

Question 5

Electric Field Strength (E)

Answer 5

Electric force per positive unit test charge (E = F/q)

Question 6

Radial Field

Answer 6

field that extends radially (like the electric field around a point charge or the gravitational field around a planet)

Question 7

Electric Potential (V)

Answer 7

work done per unit charge moving a small positive test charge in from infinity to a point in an electric field. (V = W/q) (V = kq/r)

Question 8

Electric Potential Energy

Answer 8

energy that a charge has due to its position in an electric field

Question 9

Electric Potential Difference (ΔV)

Answer 9

electric potential energy difference per unit charge between two points in an electric field (ΔV = ΔEe / q OR ΔV = W / q)

Question 10

Electronvolt (eV)

Answer 10

energy gained by an electron moving through an electric potential difference of one volt

(1 eV = 1.60 x 10^-19 J)

Question 11

Electric Current (I)

Answer 11

current is defined in terms of the force per unit length between parallel current-carrying conductors

Question 12

Resistance (R)

Answer 12

ratio of potential difference applied to a device to the current through the device (R = V/I)

Question 13

Resistor

Answer 13

device with a constant resistance (Ohmic device) over a wide range of potential differences

Question 14

Ohm’s Law

Answer 14

The current flowing through a device is proportional to the potential difference applied across it providing the temperature is constant

Question 15

Ohmic Device

Answer 15

one whose resistance remains constant over a wide range of potential differences (eg – resistor)

Question 16

Non-Ohmic Devic

Answer 16

one whose resistance does not remain constant over a wide range of potential differences

Question 17

Electromotive Force (emf) (ε)

Answer 17

Total energy difference per unit charge around a circuit

Question 18

Internal Resistance (r)

Answer 18

resistance inside a battery that causes the battery’s terminal potential difference to be less than its emf

Question 19

Ideal Ammeter

Answer 19

one with zero internal resistance – must be placed in series

Question 20

Ideal Voltmeter

Answer 20

one with infinite internal resistance – must be placed in parallel

Question 21

Potential Divider

Answer 21

two resistors placed in series that divide up the battery’s potential difference (R1 / R2 = V1 / V2)

Question 22

Negative Temperature Coefficient (NTC) Thermistor

Answer 22

Thermistor –> sensor whose resistance depends on its temperature – increase in temperature causes decrease in resistance

Question 23

Strain Gauge

Answer 23

sensor whose output voltage depends on any small extension or compression that occurs which results in a change of length

Question 24

Magnitude of a magnetic field

Answer 24

ratio of magnetic force on a current carrying conductor to the product of the current and length of wire and sine of the angle between the current and the magnetic field

Question 25

Direction of a Magnetic Field

Answer 25

the direction that the North pole of a small test compass would point if placed in the field (N to S)

Question 26

Magnetic Flux

Answer 26

product of the magnetic field strength and a cross-sectional area and the cosine of the angle between the magnetic field and the normal to the area

Question 27

Magnetic Flux Linkage

Answer 27

product of the magnetic flux through a single coil and the total number of coils

Question 28

Faraday’s Law

Answer 28

The emf induced by a time changing magnetic field is proportional to the rate of change of the flux linkage