P4 - Electric Circuits

Question 1

What is an electric field?

Answer 1

A charged object (X) creates an electric field around iteself, which causes a non-contact force on any other charged object in the field

Question 2

What are electrons?

Answer 2

Tiny negatively charged particles that move around the nucleus of an atom

Question 3

What is an ion?

Answer 3

A charged atom or molecule

Question 4

What is a line of force in an electric field?

Answer 4

Line along which free positive charge moves along in an electric field

Question 5

What are neutrons?

Answer 5

Uncharged particles of the same mass as protons. The nucleus of an atom contains both protons and neutrons

Question 6

What is potential difference?

Answer 6

A measure of the work done or energy transferred to a device by each coulomb of charge that passes through it. The unit of potential difference is the volt (V)

Question 7

What are protons?

Answer 7

positively charged particles with an equal and opposite charge to that of an electron

Question 8

What is the equation for resistance?

Answer 8

Resistance = potential difference / current

Question 9

What is the unit of resistance?

Answer 9

Ohms (Ω)

Question 10

What is static electricity?

Answer 10

Electric charge stored on insulated objects

Question 11

How can you charge an object?

Answer 11

Charge by friction, by rubbing 2 insulating materials together electrons are transferred from 1 material to the other. Materials that gain electrons become negatively charged, materials that lose electrons are positively charged

Question 12

What type of force is electrostatic force?

Answer 12

Non-contact

Question 13

What happens if 2 like charges become close to each other?

Answer 13

They repel each other

Question 14

What happens if 2 opposite charges come near each other?

Answer 14

They attract

Question 15

How do charged objects exert forces on each other?

Answer 15

A charged object creates an electric field around itself. The field is strongest closest to the object

Question 16

What happens to the strength of the electric field as distance from the charged point increases?

Answer 16

Decreases

Question 17

Draw the diagram for a positive and negative electric field

Answer 17

Question 18

Describe how a balloon can stick to a wall due to electrostatic attraction

Answer 18

A balloon is normally neutrally charged, however when rubbed against another insulator (such as a dry cloth) it will become positively or negatively charged due to gaining or losing electrons. As the balloon is now charged, the opposite charge is induced on the wall due to electrons being attracted or repelled. The wall is then attracted as opposite charges attract. This electrostatic attraction causes the balloon to stick to the wall

Question 19

Describe how a charged object can attract a neutral object

Answer 19

A charged object can attract a neutral object as it will induce a charge on the neutral object due to electrons in the neutral object being attracted or repelled

Question 20

Why can conductors not become charged by friction?

Answer 20

Conductors cannot hold the charge, as the electrons can move through them

Question 21

Why can an insulator become charged?

Answer 21

Insulators prevent the electrons from moving and the charge remains static

Question 22

What are the advantages of using static electricity to help coat a car with paint?

Answer 22

• There is less paint wasted due to the attraction of the oppositely charged paint and car body.
• The application of paint is more even over the entire car body as the entire car can be coated, even when not in the direct line of paint

Question 23

Describe how the strength of the electric field varies with distance in the electric field between oppositely charged parallel plates

Answer 23

The strength of the electric field is constant through the separation between the plates, this is because as you travel further from the positive plate, despite the strength of the positive electric field decreasing as you are further from it, the strength of the negative electric field increases as you are closer to it

Question 24

Describe the motion of a proton when placed close to a positive point charge

Answer 24

The positively charged proton will accelerate away from the positive charge due to the repulsion of the positive proton and positive point charge. However, the protons acceleration will decrease with distance from the positive point charge, this is because the electric field strength decreases with distance from the positive point charge

Question 25

Describe the motion of a proton when placed close to the positive plate in the uniform field

Answer 25

The proton will accelerate with a constant acceleration from the positively charged plate to the negatively charged plate

Question 26

What is an electric current?

Answer 26

The flow of charge

Question 27

What is the charge in a circuit carried by?

Answer 27

electrons

Question 28

What is the unit of current?

Answer 28

Amperes (Amps)

Question 29

What does 1 amp represent?

Answer 29

rate of flow of 1 coulomb per second

Question 30

What is the equation for current?

Answer 30

Current (I) = Charge (Q) / time (t)

Question 31

What is the equation for potential difference?

Answer 31

Potential difference (V) = Energy (E) / Charge (Q)

Question 32

What is resistance?

Answer 32

Electrical resistance is the opposition to the flow of charge. It is measured in Ohms

Question 33

What is Ohms law?

Answer 33

The current through a resistor at a constant temperature is directly proportional to the potential difference across the resistor

Question 34

What is used to measure current?

Answer 34

Ammeter

Question 35

What is used to measure potential difference?

Answer 35

Voltmeter

Question 36

What happens to the resistance of a wire if temperature is increased?

Answer 36

Heating the wire causes atoms to vibrate more, which in turn makes it more difficult for the electrons to flow, increasing resistance

Question 37

What charge does an electron carry?

Answer 37

Negative charge

Question 38

What is the unit of charge?

Answer 38

Coulombs (C)

Question 39

What happens to the current if you increase the resistance?

Answer 39

The greater the resistance across a component, the smaller the current that flows

Question 40

What causes sparks?

Answer 40

As static electric charge builds up on an object, a strong electric field between the charged object and the earth (or earthed object) is made. The strong electric field causes the air to become ionised as electrons are removed from the air particles. This causes the air to become conductive causing the current to flow through it. This movement of electrons is the spark you see

Question 41

What 2 forms of energy are emitted from a light bulb?

Answer 41

Useful: Visible Light Radiation
Wasted: Thermal Energy

Question 42

Explain what causes electrons to move from an area with a build up of electrons to an area without a build up of electrons

Answer 42

Due to a build of electrons and charge, there is a potential difference between the area with a build up of electrons and the area without. This causes some of the electrons to transfer to the area without a build up of electrons

Question 43

Explain how a negatively charged student receives an electric shock when they touch a metal tap:

Answer 43

There is a potential difference between the student and the tap, this causes the electrons to transfer from the student to the tap. This earths the charge causing an electric shock

Question 44

What is earthing an object?

Answer 44

the process of removing the excess charge on an object by means of the transfer of electrons between it and another object, causing the object to become neutral