Year 11 Physics Module 4: Electricity and Magnetism Practice Questions

Question 6 ⭐⭐

An electric force of 2N is resulted from two electrons interacting with one another. Determine the distance these electrons must be form one another. (3 marks)

 

(L1.3.3: apply the electric field model to account for and quantitatively analyse interactions between charged objects)

Question 7 ⭐⭐⭐

A small metal sphere with charge q1 = -3μC is held in place by a stand, a second charge q2 = -8μC and a mass 2g is approaching the sphere as in the figure. If q2 has a velocity of 20m/s at the instant shown, determine:

a) The speed of q2 when it is 0.5m from q1
b) The closest distance q2 comes to q1.

Electric Circuits

Question 8 ⭐

What is the quantity of charge in a metal with a current of 50A for 10 seconds? (2 marks)

 

(L2.1.1: investigate the flow of electric current in metals and apply models to represent current)

Question 9 ⭐

An electric circuit has a total resistance of 5Ω and a current of 3A. What is the work done by an electron in this circuit? (2 marks)

 

(L2.2: investigate quantitatively the current–voltage relationships in ohmic and non-ohmic resistors to explore the usefulness and limitations of Ohm’s Law)

Question 10 ⭐⭐

The energy used by a light bulb is 50J for each minute of use. Determine the voltage of this light bulb if the circuit containing the light bulb has a current of 2.5A. (2 marks)

 

(L2.3: investigate quantitatively and analyse the rate of conversion of electrical energy in components of electric circuits, including the production of heat and light, by applying ? = ?? and ? = ?? and variations that involve Ohm’s Law)

Question 11 ⭐⭐⭐⭐

Explain, using a relevant law, the conservation of charge within an electric circuit. (3 marks)

 

(L2.4.1: Investigate qualitatively and quantitatively series and parallel circuits to relate the flow of current through the individual components, the potential differences across those components and the rate of energy conversion by the components to the laws of conservation of charge and energy)

Question 12 ⭐⭐

If the resistors in the circuit below have resistances R1 = 6Ω, R2 = 4Ω, R3 = 8Ω, R4 = 12Ω, determine the total resistance of the circuit below: (3 marks).

(L2.4.3: investigate qualitatively and quantitatively series and parallel circuits to relate the flow of current through the individual components, the potential differences across those components and the rate of energy conversion by the components to the laws of conservation of charge and energy, by deriving the following relationships)

Question 13 ⭐⭐⭐⭐

Within the following circuit;

• The Resistance of Resistor 1 is Twice Resistor 2
• The Resistance of Resistor 3 is a Third of Resistor 2.
• The Total Resistance of the Circuit is 5Ω.

Determine the resistance of Resistor 3 (5 marks)

(L2.5: investigate quantitatively the application of the law of conservation of energy to the heating effects of electric currents, including the application of ? = ?? and variations of this involving Ohm’s Law)

Question 14 ⭐⭐

Explain how heat is unwanted in an electric circuit and how this relates to the Conservation of Energy. (3 Marks) 

 

(L2.5: investigate quantitatively the application of the law of conservation of energy to the heating effects of electric currents, including the application of ? = ?? and variations of this involving Ohm’s Law)

Magnetism

Question 15 ⭐

Question 15: Identify the possible charges on objects that have a;

• Attractive Magnetic Force
• Repulsive Magnetic Force (2 marks)

 

(L3.1: investigate and describe qualitatively the force produced between magnetised and magnetic materials in the context of ferromagnetic materials)

Question 16 ⭐

Illustrate the magnetic flux lines around a bar magnet, showing the correct direction of flux. (3 marks)

 

(L3.2: use magnetic field lines to model qualitatively the direction and strength of magnetic fields produced by magnets, current-carrying wires and solenoids and relate these fields to their effect on magnetic materials that are placed within them)

Question 17 ⭐

 Identify 2 key features of magnetic flux lines when illustrated in diagrams. (2 marks)

 

(L3.2: use magnetic field lines to model qualitatively the direction and strength of magnetic fields produced by magnets, current-carrying wires and solenoids and relate these fields to their effect on magnetic materials that are placed within them)

Question 18 ⭐⭐

 A solenoid with 200 turns per metre has a magnetic field of 20T. Determine the current flowing through the wire. (2 marks)

 

(L3.3: conduct investigations into and describe quantitatively the magnetic fields produced by wires and solenoids)

Question 19 ⭐⭐⭐

A current carrying wire moving from left to right has a magnetic field strength of 4.5 x 10^-6 T at a distance of 4cm from the wire, what is the current running through the wire?  (2 marks)

Question 20 ⭐⭐⭐🔥

Two parallel wires carry equal currents in opposite directions. 

a) Is there any place that the net magnetic field is zero? Where does this occur, or why does it not occur? 

b) Does the answer in part a) change if the currents flowed in the same direction?  (4 marks)

Question 1

Sample Answer:

When an object has no electric charge it is said to be neutral. In essence, the number of protons and electrons within the object are equivalent and thus their charges cancel each other out. However, through the process of friction, electric charge can be induced in the object. For instance, rubbing a balloon against an individual’s hair results in the transfer of electrons from hair to the balloon. As a result, there are more electrons than protons in the balloon making it negatively charged, whilst there are more protons than electrons in hair making it positively charged. This then establishes static forces between the two objects causing hair to stand up and attract to the balloon.

💡Tip: Since this is 2 marker, the expectation is only to provide ONE process, even though there are three that you can choose from including: friction, conduction and induction.

Remember that this is an explain question, so use the combination of cause + effect – i.e. use terms like ‘however; therefore’ to show that you are explaining your answer.

Question 2

Sample Answer:

Electrostatic force between two objects can be calculated using Coulomb’s Law, which states the following: F = k * (q1 * q2) / r² . Looking at this equation, there are 2 variables that can be altered, which include: 

• Distance between the Two Objects (r²): there is an indirect proportionality relationship between the distance and force (F), which means that as the distance increases, the force will decrease by a factor of 1/r². 
• Electric Charge of the Objects (q1 or q2): there is a direct proportional relationship between the electric charge of the objects and force. As electric charge increases, the force will increase by the same factor. Similarly, as a electric charge decreases, the force will decrease by the same factor. 

💡Tip: Here, 2 marks would be attributed to identifying 2 variables and then the other 2 marks are attributed to describing how these variables would alter the forces between objects. You can use dot – points in the sciences to explain your answer, so don’t be afraid to use them in your exam! They can save quite a bit of time!

Question 3

Sample Answer:

💡Tip: Since this is a 3 mark question, this is what markers are generally looking for: 

• Number of field lines equals the electric charge i.e. if one positive point charge is 1C and there are 7 field lines, then a 2C positive point charge should have 14 field lines. For simplicity’s sake, I used 2 positive point charges with the same charge. 
• Field lines should move outwards for positive charges, whilst negative charges move inwards.  
• Show a point of ‘dead space’ where there are no field lines interacting as there is a repulsive force. 
• Remember to label the diagram and also state whether or not it is to scale.

Question 4

Sample Answer:

In electric fields, there can be either positive point charges or negative point charges and each of them have their own representation (as illustrated in the diagram below):

💡 Tip:

• Number of field lines equals the electric charge i.e. if one positive point charge is 1C and there are 7 field lines, then a 2C positive point charge should have 14 field lines. 
• Field lines should move outwards for positive charges, whilst negative charges move inwards.

Question 5

Sample Answer:

💡 Tip: Key things to remember here:

• Draw a diagram to visualise what is happening in the question – many students forget this and make mistakes in identifying the direction of travel for the charged particle. 
• Always correct the significant figures at the end of the answer to the smallest number of significant figures provided by the question – in this case, it was 1 significant figure.

Question 6

Sample Answer:

💡 Tip: Key things to remember here: 

• Students often don’t write out their entire working out, but it only takes an extra couple of seconds/ question to do. It makes it easier to identify any mistakes in the answer if you write out your working, so always make sure you don’t skip too many steps in your answer! 
• Always correct the significant figures at the end of the answer to the smallest number of significant figures provided by the question – in this case, it was 1 significant figure.

Question 7

a) v = 17.13m/s

b) r = 0.477m 

Question 8

Sample Answer:

Question 9

Sample Answer:

💡 Tip: Never forget your units or significant figures – there is always 1 mark for each in the exam so don’t lose out on any easy marks!

Question 10

💡 Tip: Never forget your units or significant figures – there is always 1 mark for each in the exam so don’t lose out on any easy marks!

Question 11

Sample Answer:

The Law of Conservation of Energy states that energy cannot be created nor destroyed, rather it is transferred or transformed. This means that the amount of energy in a system remains the same. Kirchoff’s Current Law is a direct result of this, which states that all currents moving into a junction must equal all the currents moving out of the junction. Therefore, there is always current flowing in and out and does not accumulate or vanish at any point in time. 

💡 Tip: This is a difficult question as it requires knowledge about Kirchoff’s Current Law, which students sometimes skip over in the electricity section of this module. 

Question 12

Sample Answer:

Question 13

Sample Answer:

💡 Tip: Although Kirchoff’s Parallel Circuit Law is not on the formula sheet, it is important to know it! I would highly recommend going through both the parallel and series circuit laws to understand their application, especially for a question like this one!

Question 14

Sample Answer:

The Law of Conservation of Energy states that energy cannot be created nor destroyed, rather it can be transformed or transferred. As electrons move through a circuit, they lose their energy due to friction and resistance within the circuit. This energy loss is transformed in the form of heat energy, as it cannot be destroyed by the system. 

💡 Tip: Since this is a 3 mark explain question, it is important to use the ‘cause + effect’ answer style. Observe how I have used it in this question and how the LOCOE is added in to explain how energy is lost as heat in the circuit. 

Question 15

Sample Answer:

• North Pole (positive) and South Pole (negative) = Attractive Magnetic Force
• North Pole (positive) and North Pole (positive) = Repulsive Magnetic Force 

Question 16

Sample Answer:

💡 Tip: Remember here to add a title and draw equal magnetic flux lines coming out of the bar magnet from both the north and the south pole. See answer for next question for any extra comments!

Question 17

Sample Answer:

• Number of field lines should match/ be proportional to the magnetic field strength. 
• Magnetic field lines starting from the north pole move outwards towards the south pole. Ensure that there is equal spacing in between the field lines and that they are not clustered coming out from one spot. 

Question 18

Sample Answer:

Question 19

Sample Answer:

Question 20

Sample Answer:

a) At the centre, between the two parallel wires will have a net magnetic field of zero as the fields are equal in magnitude but are orientated in the opposite direction. 

b) Yes, then as the fields are orientated in the same direction, there will be no region where there is zero net field. 

💡 Tip: To visualise the answer, I would recommend students to draw out a diagram to illustrate what is happening in the question.