Module 6

Question 1

Capacitance

Answer 1

Charge stored per unit pd on the positive plate of a capacitor.

Question 2

Farad

Answer 2

One coulomb per unit volt.

Question 3

Time Constant

Answer 3

The time taken for the pd (or current, or charge) to decrease to e^-1 (37%) of its initial value.

Question 4

Coloumb’s Law

Answer 4

Any two (point) charges exert an electrical force on each other that is directly proportional to the product of their charges and inversely proportional to the square of the separation between their centres.

Question 5

Electric Field Strength

Answer 5

Force per unit positive charge at a point in an electric field.

Question 6

Electric Potential

Answer 6

The work done per unit charge in bringing a positive charge from infinity to a point in the electric field.

Question 7

Magnetic Flux Density

Answer 7

The force per unit current and per unit length of a current-carrying conductor perpendicular to a uniform magnetic field.

Question 8

Tesla

Answer 8

The magnetic flux density is 1 Tesla when a conductor carrying a current of 1A, perpendicular to a uniform magnetic field, experiences a force of 1N per metre of its length.

Question 9

Magnetic Flux

Answer 9

Magnetic flux density x Area perpendicular to the magnetic field.

Question 10

Magnetic Flux Linkage

Answer 10

Magnetic flux x Number of turns of the coil.

Question 11

Weber

Answer 11

One tesla metre squared.

Question 12

Faraday’s Law of Electromagnetic Induction

Answer 12

The induced emf is directly proportional to the rate of change of magnetic flux linkage.

Question 13

Lenz’s Law

Answer 13

The direction of the current induced in a conductor by a changing magnetic field is such that it creates a magnetic field that opposes changes in the initial magnetic field.

Question 14

Activity

Answer 14

The rate of decay of the radioactive nuclei.

Question 15

Decay Constant

Answer 15

The probability of decay of a nucleus per unit time.

Question 16

Annihaltion

Answer 16

The process of a particle and its antiparticle colliding and being converted into energy in the form of photons.

Question 17

Pair Production

Answer 17

The process of a single high energy photon decaying into a particle and antiparticle.

Question 18

Binding Energy of a Nucleus

Answer 18

The minimum energy required to separate all protons and neutrons of a nucleus.

Question 19

Half Life

Answer 19

The average time taken for half of the nuclei in a radioactive sample to decay.

Question 20

Mass Defect

Answer 20

Mass of a nucleus - Total mass of constituent protons and neutrons.

Question 21

Ultrasound

Answer 21

A longitudinal sound wave with frequency greater than 20kHz.

Question 22

Comptom Effect

Answer 22

An x-ray photon interacts with an orbital electron within the atom. This electron is ejected, and the photon is scattered with lower energy.

Question 23

Piezoelectric Effect

Answer 23

Applying an alternating pd to a quartz crystal causes it to vibrate and emit x-ray photons.

Question 24

Acoustic Impedance Matching

Answer 24

The acoustic impedances of media at a boundary are similar, and so less ultrasound is reflected.