Physics

Question 1

Describe how static builds up

Answer 1

Static builds up by friction. When insulating materials are rubbed against one another, electrons move from one to another, leaving one object with a positive charge and one with a negative charge.

Remember, only ELECTRONS move - positive charges do not!

Question 2

Define current and give its unit

Answer 2

Current is the flow of electrons around a circuit

Current is measures in Amps

Question 3

Define potential difference and give its unit

Answer 3

Potential difference (AKA voltage) is the driving force that pushes current round

PD is measured in Volts

Question 4

Define resistance and give its unit

Answer 4

Resistance is anything in the circuit which slows flow down

Resistance is measured in Ohms

Question 5

What is charge measured in, and how does it relate to current?

Answer 5

Charge is measured in Coulombs

Charge = Current x Time

Question 6

What is a diode?

Answer 6

A diode allows current to flow freely in one direction (but not the other)

Question 7

What is an LED?

Answer 7

An LED is a diode that emits light when current is flowing through it in the forward direction

Question 8

How does a thermistor work and when are they used?

Answer 8

Thermistors decrease resistance as temperature increases. They are useful in thermostats and temperature detectors.

Question 9

Define the term ‘half-life’

Answer 9

Half life is the average time it takes for the number of nuclei in a radioactive isotope sample to halve

Question 10

The activity of a radioactive sample is 640Bq. Two hours later it has fallen to 40Bq. Find its half life.

Answer 10

Divide 640/2 and keep dividing by 2 until you reach 40.

= 4 half lives

4 half lives = 2 hours (as the question told you) so divide 2 hours by 4…

Answer = 30 minutes

Question 11

What is an alpha particle? What is an alpha particle blocked by?

Answer 11

Alpha particles are Helium nuclei.

Alpha particles are heavy, don’t penetrate very far and are blocked by paper

Question 12

What is a beta particle? What is a beta particle blocked by?

Answer 12

Beta particles are electrons.

Beta particles are lighter than alpha particles, more penetrating and are blocked by thin aluminium.

Question 13

What is a gamma ray?

Answer 13

Gamma rays are short wavelength electromagnetic waves

These are the most penetrating of the types of radiation and are stopped by a thick layer of lead

Question 14

How does nuclear fission work?

Answer 14

In nuclear fission, a neutron is absorbed into a nucleus, which causes the nucleus to split, releasing lots of energy and more neutrons, which continue this effect as this hit other nuclei.

Question 15

How do control rods work in nuclear fission?

Answer 15

Control rods absorb neutrons, slowing down the reaction

Question 16

How does nuclear fusion work?

Answer 16

Nuclear fusion is the joining of 2 small atomic nuclei (e.g. 2 hydrogen atoms to form a helium), releasing lots of energy

Question 17

What is the main disadvantage of nuclear fusion?

Answer 17

Nuclear fusion requires lots of heat and pressure, as to join 2 positively charged atoms together means electrostatic repulsion of protons needs to be overcome. Nuclear fusion is nearly impossible on earth and is not yet done.

Question 18

What is the difference between speed and velocity?

Answer 18

Speed is just how fast something is travelling e.g. 30mph

Velocity must include direction e.g. 30mph north

Question 19

What units is velocity measured in?

Answer 19

Velocity is measured in m/s or km/h or mph, the same units as speed

Question 20

What is the strength of gravity on earth?

Answer 20

10N/kg

Question 21

What is earthing?

Answer 21

Earthing is connecting a charged object to the ground using a conductor

Question 22

Describe a situation where the separation of electric charge could cause a spark

Answer 22

When refuelling an aircraft, a spark could occur between the fuel pipe and aircraft if the aircraft is not earthed

Question 23

Momentum is measured in which units?

Answer 23

kg m/s

Question 24

Gravity is measured in which units?

Answer 24

Newtons

Question 25

Gravitational potential energy is measured in which units?

Answer 25

Joules

Question 26

What is terminal velocity?

Answer 26

Terminal velocity is maximum velocity, reached when the forces acting something are balanced (e.g. gravitational pull down and drag)

Question 27

Describe what happens to the nuclei in a nuclear fusion reactor

Answer 27

Two or more nuclei combine to produce a large nucleus

Question 28

Explain why dust particles settle on charged metal plates

Answer 28

Dust settles because the plates have an opposite charge to the dust particles, so they settle due to the force of attraction

Question 29

Explain why people that live close to sources of radon gas have an increased health risk due to background radiation

Answer 29

Radon is radioactive and emits alpha radiation. Radon can be inhaled into the lungs and it can cause mutations inside the body, which damage the cells and may lead to cancer.

Question 30

Explain why a light-dependent resistor can help preserve energy stored in a battery

Answer 30

Less current is used in darkness, as resistance increases with less light. Less current means less energy is transferred per second, therefore energy is preserved.