CH5 + CH6

Question 1

What is direct current?

Answer 1

Current which flows in one direction.

Question 2

What is alternating current?

Answer 2

Current which repeatedly reverses its direction of flow.

Question 3

What is the live wire?

Answer 3

Wire which is alternately positive and negative every cycle.

Question 4

What is the neutral wire?

Answer 4

Wire which is at zero volts.

Question 5

What is the peak potential difference of an a.c supply?

Answer 5

Maximum voltage measured from zero volts.

Question 6

How can the frequency of an a.c supply be measured?

Answer 6

1 / time taken for 1 cycle

Question 7

What are sockets and plugs made out of and why?

Answer 7

Plastic and tough materials - electrical insulators to prevent electrocution.

Question 8

What is a mains cable made up of?

Answer 8

Two or three insulated copper wires surrounded by flexible plastic material.

Question 9

What colours are the live wire, neutral wire and earth wire.

Answer 9

Brown, blue and yellow and green.

Question 10

Why is there an earth wire?

Answer 10

To stop the metal case becoming live if the live wires breaks, preventing electrocution.

Question 11

What is the power supplied to a device?

Answer 11

The energy transferred to it each second.

Question 12

What is the energy transferred to a device?

Answer 12

E (energy in joules) = P (power in watts) x t (time in seconds)

Question 13

What is the electrical power supplied to an appliance?

Answer 13

P (power in watts) = I (resistance in ohms) x V (current in amperes)

Question 14

What is the charge flow?

Answer 14

Q (charge flow in coulombs) = I (current in amperes) x t (time in seconds)

Question 15

What happens to the temperature of a resistor when charge flows through it?

Answer 15

Energy is transferred to it, making it hotter.

Question 16

What is the energy transferred to a component?

Answer 16

E (energy in joules) = V (potential difference in volts) x Q (charge flow in coulombs)

Question 17

When charge flows around a circuit for a given time, what is the energy supplied by the battery equal to?

Answer 17

The energy transferred to all the components in the circuit.

Question 18

What does a domestic electricity meter measure?

Answer 18

How much energy is supplied.

Question 19

What is density equal to?

Answer 19

Density (kg/metres cubed) = mass (kg) / volume (metres cubed)

Question 20

How is the density of a solid/liquid found?

Answer 20

By measuring the mass and the volume and using the density equation.

Question 21

What happens if an object with a lower density than water is placed on water?

Answer 21

It will float.

Question 22

How are particles arranged in a solid?

Answer 22

Tightly packed together, vibrate about a point and have the least energy.

Question 23

How are particles arranged in a liquid?

Answer 23

Move about randomly, in contact with eachother and are more energetic than particles in a solid.

Question 24

How are particles arranged in a gas?

Answer 24

Move about randomly, are far apart and have a low density and are the most energetic.

Question 25

Does the mass change during change of state?

Answer 25

No. The mass stays the same because the number of particles is unchanged.

Question 26

What is melting point?

Answer 26

The temperature in which a substance melts/solidifies.

Question 27

What is boiling point?

Answer 27

The temperature in which a substance boils/condenses.

Question 28

What is needed to melt a solid or boil a liquid?

Answer 28

Enough energy.

Question 29

What is the difference between boiling and evaporation?

Answer 29

Boiling occurs throughout a liquid at its boiling point. Evaporation occurs at the surface when its temperature is below its boiling point.

Question 30

What effect does increasing the temperature of a substance have on its internal energy?

Answer 30

The internal energy increases.

Question 31

What happens when a substance is heated?

Answer 31

Kinetic energy of its particles increases.

Question 32

What happens when a substance melts or boils?

Answer 32

If it melts or it boils, the potential energy of its particles increases.

Question 33

What causes the pressure of a gas on a surface?

Answer 33

Particles of a gas constantly hitting the surface.

Question 34

What is latent heat?

Answer 34

The energy needed for a substance to change its state without changing its temperature.

Question 35

What is specific latent heat of fusion (or vaporisation)?

Answer 35

The energy needed to melt (or boil) 1kg of a substance without changing its temperature.

Question 36

What is the equation for latent heat calculations?

Answer 36

E (energy) = m (mass in kg) x l (specific latent heat in J/kg)

Question 37

How is the specific latent heat of ice or water measured?

Answer 37

Using a low-voltage heater to melt the ice (or boil the water).

Question 38

If the temperature of a gas in a sealed containter increases, what will happen to the pressure of the gas?

Answer 38

It will increase - the molecules move faster so they hit the surfaces with more force. The number of impacts per second of gas molecules on the surfaces increases, so the total force of the impacts increases.