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Question 1

Why do metals, soluble salts, and water conduct easily?

Answer 1

Metals conduct easily because of the highly mobile “sea” of electrons.
Soluble salts condct easily because of the mobile ions
Water conduct quite well because some of the h2o molecules dissociate to form OH- and H3O+ ions

Question 2

Why are some substances a good insulator? Give an example.

Answer 2

Glass is an insulator because any free electrons or ions cannot flow within the glass.
more e.gs: plastic

Question 3

What do we refer as conductors?

Answer 3

We generally refer to substances as conductors or insulators at low voltages. (anything can conduct at high voltages or the distance is small enough)

Question 4

What are sparks and lighting?

Answer 4

light given off when air is made to conduct.

Question 5

cell

Answer 5

a device that contains two substances with different electron affinities

Question 6

separation of charges=?

Answer 6

potential electrical energy
charges flow, energy follows when positive is connected to the negative side

Question 7

battery

Answer 7

stack of cells

Question 8

current electricity

Answer 8

the study of moving electrical charges, and the transfer and transformation of energy

Question 9

early type cell

Answer 9

zinc carbon

Question 10

two main characteristics of batteries

Answer 10

• voltage= correct term is actually electro-motive force(emf), which is a measure of the amount of push force on the electrons, originally called electrical pressure.
• amp hours= difference between d cells and c cells on a AA

Question 11

forces on the electrons at each stage that prevents them from flowing

Answer 11

At the positive terminal= electrons in wire are attracted to the positive terminal, but they are also attracted to the cations in the wire, so can’t move
At the negative terminal= stored electrons in the battery will push against the electrons already in the wire (but nowhere for them to go)

Question 12

forces on the electrons at each stage that allows them to flow

Answer 12

At the positive terminal= electrons in the wire are attracted to the positive terminal
At the negative terminal= the stored electrons in the battery will push against the electrons already in the wire
There is a complete circuit so the electrons can now flow

Question 13

conventional current

Answer 13

we pretend that imaginary positive charges flow in the opposite direction (the non pretended one is the electron flow

Question 14

current

Answer 14

rate of flow of positive charges
has symbol “i”
measured in amps, symbol “a”
fundamental SI quantity
measured by a device called the ammeter
indicate by an arrow in wire

Question 15

charge

Answer 15

• property of a body
• symbol q or Q

Question 16

Amp

Answer 16

1 coulomb of charge flow past per second

Question 17

An airplane travelling horizontally with a velocity of 125 ms^-1 is at an altitude of 1.35 km
when it drops a 25.7 kg package to the ground below. (assume that there is no air resistance)
(c) Calculate the kinetic energy of the package as it hits the ground. (1 mark)

Answer 17

Ek= 340357 + 200781= 541139
= 5.41 *10^5 J

Question 18

Discuss the energy changes in each of the following situations:
(a) A petrol engine car is accelerating up a hill.
(2 marks)

Answer 18

Potential chemical energy converted to
1. Ek (car accelerating)
2. E GPE (car increasing height)
3. Heat (friction and air resistance)

Question 19

Discuss the energy changes in each of the following situations:
A skydiver falling at terminal velocity (2 marks)

Answer 19

v constant-> no increase in Ek
E GPE converted to heat (air resistance)

Question 20

Question 3
When a school bag of mass m is lifted straight upwards from the floor onto a table (h metres from the floor) in t seconds a certain amount of work is done on the bag. There is also a certain average power input to the bag.
For each of the following variations to this, state how
the new values of work and power will compare with the original ones.
Use the terms less, the same, or greater in the spaces provided in the table below to answer the question.
(3 marks)

Variation Work done Power input to bag
on the bag

It takes twice as long to lift
the bag. (h and m are the
same)
The height of the table is
greater (t and m are the
same)
Lift the bag 0.5m above the
table then put it down on the
table. (t, h and m are the
same)

Answer 20

Work done on the bag:
w= mgh same
greater
same

Power input to bag:
p= w/2t less
greater
same

Question 21

A desk of mass 40.0 kg has to be shifted a distance of 3.10 m across a section of carpet.
(b) If you could lift the desk to move it rather than just dragging it, would you end up doing
more work than *A? Explain, using a calculation to assist. You may have to make
some assumptions. (2 marks)

*A= work done to overcome friction while dragging it: 173.6 J

Answer 21

Assume that you lift the desk 5 cm
Ep= mgh= 40.0 * 9.81 * 0.05= 19.6 J
therefore less energy needed to lift & move

Question 22

Question 9A 2023 mut
When sections of the London Underground railway were being constructed, the track at the stations was built at a higher level than the track between the stations, as shown in the diagram below.
(a) Explain, using energy concepts, the advantages of this arrangement in terms of fuel saving and wear on brakes. (2 marks)

Answer 22

• The train will slow up the incline meaning that the brakes will be used less. Less Ek to heat.
• The train will accelerate down the decline (converting Ep to Ek) without using fuel.

Question 23

Question 9b 2023 mut
(b) To help analyse the motion of the train, for different numbers of passengers, engineers
model the train as a ball rolling up an incline.
Assume that the ball always travels at 13 ms-1
in the section AB, the track is frictionless, and
there is no air-resistance. How would the ball’s velocity at C differ if the ball’s mass was
larger. (ie there were more people on the train and so the trains mass increased). Explain.
(2 marks)

Answer 23

From B to C Ek converting to Ep
Ep= mgh Ek= 1/2 mv^2
therefore gh=1/2v^2 (m cancelled out)
therefore v=sqrt2gh (independent of mass)
the velocity will be the same for any mass

Question 24

In a hydroelectric power plant, water falls at a rate of 1300 kg/s from a height of 125 m.
Assuming that 60% of the energy of falling water is converted into electrical energy,
calculate the power output of the plant.
(3 marks)

Answer 24

Every second Δ Ep= mgh= 1300 * 9.81 * 125
= 1.59 mJ
W= 0.60 * Δ E= 9.56 10^5 J
P= w/t= 9.5610^5/1= 9.6*10^5

Question 25

Two figure skaters, Sam (with a mass of 70.0 kg) and Olivia (with a mass of 53.9 kg), are
embraced and are moving with a constant velocity of 5.0 ms-1 west. They push off from each
other and, after they separate, Sam has a velocity of 2.0 ms-1 west. Calculate Olivia’s velocity
after they separate.
(3 marks)

Answer 25

P before= mb= (70.0 + 53.9) 5.0= 619.5 kgms^-1
P after= MsVs + MoVo= 2.070.0+ Vo*53.9
P conserved
therefore 619.5= 140+ 53.9 Vo
therefore Vo= 8.896
= 8.9 ms^-1 west

Question 26

A 3350 kg 4WD vehicle moving at 6.0 ms-1 east collides with a small Hyundai i20 car of mass 1580 kg moving west at 8.0 ms-1. The 4WD and the car couple after the collision.
(c) Without calculation, comment on the change in momentum of each vehicle.

Answer 26

from NIII F 4wd on car= F car on land
from NII F= ΔP/T but t is the same
therefore ΔP 4wd= ΔP car

Question 27

One method used to generate energy is hydroelectric power, where water is collected in high elevation dams and run through low lying electrical generators or turbines.
A dam in Tasmania stores 1.8 x 109 kg water every 24 hours. This is released into a turbine 180 m below the dam.
a) What is the theoretical amount of electrical energy that can be generated in 24 hours. (2 marks)

Answer 27

Ep = mgh
Ep = 1.8 x 109 x 9.81 x 180
Ep = 3.2 x 1012 J (2 s.f.)

Question 28

One method used to generate energy is hydroelectric power, where water is collected in high elevation dams and run through low lying electrical generators or turbines.
A dam in Tasmania stores 1.8 x 109 kg water every 24 hours. This is released into a turbine 180 m below the dam.

• When the 1.8 x 109 kg of water drops the 180 m to the generator, it is found to create 1.43 TJ
  of electrical energy.

c) Calculate the power output from the turbine. (2 marks)

Answer 28

P = ΔE/t
P = 1.43 x 10^12/ 24 x 60 x 60
P = 1.7 x 107 W (2 s.f)

Question 29

tasc 2022 12d
Another method of generating reliable energy is wind turbines combined with pumped hydroelectric storage.
The image below outlines the process where a wind turbine powers a water pump, which is used to fill an elevated dam.
d) What energy changes are occurring in this pumped hydroelectric system? (2 marks)

Answer 29

Ek from the wind is converted into electrical energy
that powers the water pump that lifts the water into
the dam creating Ep.
The water stored in the dam drops, increasing its Ek,,
which in turn drives a turbine that converts the
energy into electrical energy.
The water can then be lifted again by the energy from
the wind turbine continuing the process.
An alternative approach is a diagrammatic
representation, provided it is ‘understandable’.

Question 30

TASC 2022 Q13
Using circuit notation, sketch a circuit showing a battery connected to a resistor. A current
flows through the resistor. Include a voltmeter and ammeter in the circuit to correctly read the
voltage across, and current through, the resistor. (2 marks)

In the circuit you have designed, if you used a 1.5 V battery and a 6.0 ohm resistor, what is
the reading on the:
i. Voltmeter:
ii. Ammeter:

Answer 30

diagram ans in photos

i V = 1.5 V
ii I = 𝑉/𝐼 = 1.5/ 6.0 = 0.25 A

Question 31

If electrical energy costs 24.697 c per kWh, calculate the cost of running the 20 W light
system for one full day. Give your answer to the nearest cent. (2 marks)

Answer 31

20 W = 0.020 kW
E = Pt = 0.020 x 24
= 0.480 kW
Cost = 24.697 x 0.480
= 11.85 cents
≈ 12 cents (nearest cent)

Question 32

TASC 2022 Q14
D) LED’s are non-ohmic resistors. What aspect of the graph suggests that the Red LED is nonohmic? (1 mark)

Answer 32

Non-ohmic resistors do not have a constant
resistance at all applied voltages.
On the graph this is indicated as a non-linear graph.

Question 33

TASC 2022 Q14
E) At a potential difference of 2.0 V, which of the three coloured diodes has the greatest
resistance? Explain your reasoning.

Answer 33

V = IR
∴ R = V/I
∴ resistance is highest when current is lowest, so
the blue diode has the greatest resistance.
(Actual values can be calculated, obtaining
22 Ω, 50 Ω and 200 Ω at 2 V for red, green and blue
respectively.)

Question 34

WEP WS 1 Q46(diagram in photos)
Describe the energy changes as the pole vaulter moves from rest at A to B, from B
to C, from C to D and from D to E.

Answer 34

At A zero EK and zero Ep. At B all EK -> elastic Ep.
At C EK is decreasing as Ep increases. At D all Ep.
At E all EK until work is done on the mat.
AT ALL TIMES TOTAL ENERGY IS CONSTANT

Question 35

Why is it necessary for the vaulter to have quite a long run-up?

Answer 35

To gain Ek to turn into Ep (elastic) in pole later.

Question 36

c Describe the role the pole plays in the energy conversion processes in pole vaulting.

Answer 36

(c) EK to convert to elastic Ep for the pole so that upwards EK can be achieved.

Question 37

What is the source of the energy that re-models the front of the car and scatters stones in all
directions.

Answer 37

EK -> work done on stones

Question 38

Work is defined in physics as…

Answer 38

1. Change in energy of a body
2. Force applied multipled by the displacement in the direction of the vector of the force

Question 39

Work is usually defined ______ a force. Give an example as well.

Answer 39

Against. E.g. lifting an object is working against gravity

Question 40

A closed system is…

Answer 40

A region that does not exchange energy or matter with outside regions, and is not subject to external forces.
The only perfectly closed system is the universe.

Question 41

What is the principle of conservation of energy?

Answer 41

Energy is neither created nor destroyed.

Question 42

A 55.0 kg athlete steps off a 10.0 m high platform and drops onto a trampoline. As the trampoline stretches, it brings him to a stop 1.00m above the ground.
How much energy must have been momentarily stored in the trampoline when he came to rest?

Answer 42

4850j

Question 43

A wad of putty is thrown against a wall as shown. The wad of putty sticks against the wall
Which of the following statements best applies the application of the law of conservation of energy to this collision?
a) all energy has been lost
b) kinetic energy is converted to heat
c) kinetic energy is converted to momentum
d) kinetic energy is converted to potential energy

Answer 43

b

Question 44

During a game of rugby league, a 98 kg ball
carrier running northward at 3.7 m s-1
is tackled by an 84 kg opponent tackler running
south at 4.8 m s-1. The pair collide and are
held together during the encounter.

iii. Is this an elastic collision? Justify your answer.

Answer 44

No.
As Ek is not conserved.

Question 45

During a game of rugby league, a 98 kg ball
carrier running northward at 3.7 m s-1
is tackled by an 84 kg opponent tackler running
south at 4.8 m s-1. The pair collide and are
held together during the encounter

info:
v after collision: 0.2197802198
p of ball carrier before collision: 360 kgms^-1
p of tackler before collision: 400 kgms^-1
total Ek before collision: 1638 j

ii. Calculate the kinetic energy of the combined players after the collision.

Answer 45

Ek = ½mv2
Ek = ½ x (98 + 84) x 0.222
Ek = 4.4 J

Question 46

A heavily laden car has an increased mass and uses its brakes to stop. How would the
temperature of the brakes of this car compare with the temperature of the brakes of an
unladen car if stopping from the same speed? Justify your answer. (2 marks)

Answer 46

The heavier ladden car’s brakes would be hotter than the brakes of the unladen car.
As the heavy car (i.e. greater mass) has more kinetic energy, more work was done by the brakes to stop the car and more energy converted to heat through
friction. (Assume the stopping distance is about the
same.)

Question 47

A student sets up a bottle rocket which is filled with a volume of water, fitted with a cork, and then
pumped with air using a bicycle pump.
When there is enough pressure in the bottle, the cork and water is blasted downwards and the
bottle is launched upwards.
After all the water has left the bottle, the bottle is travelling upwards at 10.0 m s–1
, rising to a maximum height before falling back to earth.

After all the water has left the bottle, describe the energy transformations of the bottle during
its flight. (2 marks)

Answer 47

Bottle has kinetic energy initially and, as it gains height,
gravity does work converting kinetic energy
progressively into gravitational potential energy.
At max height it has no Ek (v = 0) and Ep. is at a
maximum.
As it falls Ep is transformed back into Ek.

Question 48

A player swings her hockey stick so that the head of the stick hits a ball that is initially stationary.
During the collision:
- The head of the hockey stick has a mass of 0.440 kg.
- The mass of the ball is 160 g.
- The velocity of the head of the hockey stick changes from 40.0 ms^ -1 E to 28.5 ms^-1 E immediately after hitting the ball.
- The ball moves off horizontally.

info: p(just before the player hits the ball)= 17.6 kgms^-1 E

(b) Determine the velocity of the ball immediately after it is hit. (2 marks)

Answer 48

P ini= Pstick + Pball
= (17.6 + 0) = 17.6 kgms^-1 east
Pfin= Pstick + Pball
= (0.440 * 28.5)+(0.160 * x)
= 12.54 + 0.160x kgms^-1 east
By law of conservation of momentum
Pini= Pfin
17.6 = 12.54+0.160x
0.160x= 5.06
x=31.6 ms^-1
Velocity of ball is 31.6 ms^-1 east

Question 49

A player swings her hockey stick so that the head of the stick hits a ball that is initially stationary.
During the collision:
- The head of the hockey stick has a mass of 0.440 kg.
- The mass of the ball is 160 g.
- The velocity of the head of the hockey stick changes from 40.0 ms^ -1 E to 28.5 ms^-1 E immediately after hitting the ball.
- The ball moves off horizontally.

(c) The collision between the stick and the ball is inelastic. Explain the meaning of this term.

Answer 49

Inelastic collision means that the total Ek before collision is NOT the same as the total Ek after collision. It’s usually as a result of some Ek being converted to heat, sound, or Ep.

Question 50

A cyclist moves 36.0 m up a slope from points A to B. During this time her speed decreases from
6.00 m s-1
to 3.00 m s-1 and her vertical height increases by 1.30 m. The combined mass of the
bicycle and the cyclist is 92.0 kg.

(b) Calculate the change in kinetic energy of the cyclist and her bicycle when moving from A to B.
(2 marks)

Answer 50

Δ Ek= 1/2mv^2 - 1/2mu^2
= 1/2 * 92 (3.00^2- 6.00^2)
= -1242J (-1.24 kJ)

Question 51

A cyclist moves 36.0 m up a slope from points A to B. During this time her speed decreases from
6.00 m s-1
to 3.00 m s-1 and her vertical height increases by 1.30 m. The combined mass of the
bicycle and the cyclist is 92.0 kg.

The cyclist peddles continuously for 8.00 s. During this time, she moves 36.0 m up the slope from
A to B, with 670 J of energy used to overcome frictional forces.

(d) Determine the useful power delivered to the bicycle by the cyclist. (3 marks)

info:
Δ Ep= 1173j
Δ Ek= -1242j
Wf= 18.6 N

Answer 51

Total work done by cyclist= (ΔEp + Δ Ek + WF)
= 1173- 1242+670)J
= 601 J
P=W/t= 601/8.00 = 75.1 watts

Question 52

Discuss the energy changes in: a ruler vibrating on a desk.
Diagram in photos. (points top to down a-c, ruler bending between those points)

Answer 52

Esp= spring potential energy
At A, Ek=0, Esp is max
A-> B: Esp converted to Ek
B: Ek=max, Esp=0
B-C： Ek converted to Esp
Some energy converted to sound and heat.

Question 53

A 2560 kg SUV travelling at 105 ms-1 hits a 1040 kg sedan travelling at 89 ms-1 in the
opposite direction. The vehicles stay coupled after the collision.
(a) What is the velocity of the wreckage immediately after impact?

Answer 53

Pbefore= Psuv +Pcar= 2560 * 105 + 1040 (-89)= 176240
Pafter= 3600v
v= 48.95
= 49 ms^-1

Question 54

A 2560 kg SUV travelling at 105 ms-1 hits a 1040 kg sedan travelling at 89 ms-1 in the
opposite direction. The vehicles stay coupled after the collision

Info: v after wreckage= 48.95 ms^-1

(b) Determine if the collision elastic? (2 marks)

Answer 54

Beofre Ek= Eksuv+ Ekcar
= 1/2 2560 (105)^2 + 1/2 1040 (89)^2= 1.82 x 10^7
After Ek = 1/2 3600 (48.95)^2 = 4.31 x 10^6
Therefore Ek not conserved, thus inelastic.

Question 55

A box of mass 18 kg is being dragged along the floor of a warehouse at a constant velocity
by a rope which supplies a force of 8.0 N at an angle of 15 degrees to the horizontal. How much work is done if the box is dragged for a distance of 25 m?
(2 marks)

Answer 55

W= Fdrag x 5 = 7.727 x 25 = 193 = 190 J
Cos 15= Fdrag/8.0
Fdrag= 8.0 cos 15
= 7.727

Question 56

Question 15
During a game of rugby league, a 98 kg ball
carrier running northward at 3.7 m s-1
is tackled by an 84 kg opponent tackler running
south at 4.8 m s-1. The pair collide and are
held together during the encounter.
Calculate the total kinetic energy of the two players before the collision. (1 mark)

Answer 56

Ek = (½ x 98 x 3.72) + (½ x 84 x 4.82)
Ek = 1638 J
Ek = 1600 J (2 s.f.)

Question 57

How many volts do powerpoints give out?

Answer 57

240v

Question 58

When a man jumps ashore from a boat, the boat is simultaneously driven away from the
bank.
(a) How is this explained?

Answer 58

In the case of a man jumping ashore from a boat, the boat-man system is considered a closed system, assuming there are no external forces acting on it (like wind or water resistance). Before the man jumps, the boat and the man are both at rest or have a net momentum of zero.

When the man jumps ashore, he exerts a force on the boat in one direction. According to Newton’s third law of motion, for every action, there is an equal and opposite reaction. So, when the man exerts a force on the boat in one direction (pushing himself away from the boat), the boat exerts an equal and opposite force on the man in the opposite direction.

As a result, the boat acquires some momentum in the direction opposite to that of the man’s jump. This causes the boat to move away from the shore. Meanwhile, the man also acquires some momentum in the direction of his jump, allowing him to land ashore.

The important thing to note is that the total momentum of the boat-man system remains constant. It’s just redistributed between the man and the boat as they move in opposite directions, in accordance with the conservation of momentum.

Question 59

Use the Law of Conservation of Momentum to explain why
(a) an astronaut moves backwards when throwing a hammer in space.

Answer 59

In summary, when the astronaut throws the hammer in space, they experience a backward motion due to the conservation of momentum. The astronaut’s backward motion is a reaction to the forward motion of the hammer, ensuring that the total momentum of the astronaut-hammer system remains zero before and after the throw. This scenario demonstrates the principle of action and reaction as described by Newton’s third law and the conservation of momentum in a closed system.

Question 60

You are standing on a stationary skateboard and attempt to step off forwards. Explain the
skateboard shooting off backwards in terms of momentum conservation AND Newton’s
third law.

Answer 60

• in a closed system (one without external forces), the total momentum before an event must equal the total momentum after the event.
• In this scenario, the closed system consists of you and the skateboard initially at rest. Since the total momentum is zero (both you and the skateboard are at rest), the total momentum must remain zero after your action.
• When you attempt to step off the skateboard forwards, you push the skateboard in one direction.
• According to Newton’s third law, the skateboard exerts an equal and opposite force on you. This force on you causes you to move forward, while the equal and opposite force on the skateboard causes it to move backward.

Question 61

Work is done when a force causes an object to ______

Answer 61

undergo displacement

Question 62

Energy of a body determines its ability to ______

Answer 62

do work

Question 63

The amount of potential energy the object possesses is equal to ____

Answer 63

the work done in lifting the object to that level.

Question 64

work is ______ of energy.
elaborate.

Answer 64

transfer
- when work is being done on an object, its energy level changes.
- if an object has a change in energy, then work must have been done on it.

Question 65

What is inelastic energy?

Answer 65

A collision which loses mechanical energy as heat or sound.

Question 66

What is power?

Answer 66

Rate of doing work.

Question 67

What is current electricity?

Answer 67

The flow of free electric charges through a conductor.

Question 68

Is charge a fundamental or derived quantity?

Answer 68

Derived. Because it’s calculated with I*T

Question 69

What is current? Is it fundamental or derived?

Answer 69

rate of flow of electrical charge. fundamental because it doesn’t derive from other base quantities.

Question 70

What does an ammeter do?

Answer 70

Measures the current passing through a point in an electrical current.

Question 71

Is electric charge ever used up?

Answer 71

No. As electrons do not disappear, energy is used up however.

Question 72

What does emf tell us?

Answer 72

how much energy is given to each coulomb of charge delivered by the battery.

Question 73

What direction does electric current flow out from a battery?

Answer 73

From the positive terminal (longer line in a battery), in towards the negative.

Question 74

Electric current flows from a region of ____ to a region of _____. What is this difference called?

Answer 74

High energy to low energy. Potential difference, aka. voltage.

Question 75

A potential difference of 6 volts between two points means…

Answer 75

each coulomb of charge will lose or dissipate 6 joules of energy as it moves between the points, which becomes heat energy or similar.

Question 76

What does a voltmeter measure?

Answer 76

The difference in electrical energy between two points in the circuit- potential difference. (usually before and after a resistor or other component)

Question 77

What’s the difference in current transmission in a series connection and in a parallel connection?

Answer 77

In a series connection, all the current passes thru both components. While in a parallel connection, the current is split between the two branches (amount in each branch depends on the resistances).

Question 78

Why’s the difference between the location of where an ammeter and a voltmeter are connected in a circuit?

Answer 78

Ammeters are connected in series with the component being measured. Voltmeters are connected in parallel with the component being measured.
- ammeters are designed to let current flow without interruption therefore have a very low resistance, therefore easy for too much current to pass thru and burn it out
- voltmeters have a very high resistance so all the current should pass through it, therefore less likely to burn-out.

Question 79

What is the maximum safe amount of current and what’s the fatal amount?

Answer 79

1 mA
100 mA

Question 80

What’s the difference between ohmic and non-ohmic conductors?

Answer 80

ohmic: linear relationship, resistance remains constant as voltage varies
non-ohmic: non-linear relationship, resistance changes as the voltage varies

Question 81

Col elec pp q1cii
(circuit: 4v power supply, 20 ohm and 40 ohm resistor placed in series)
what would be shown on the voltmeter that measures the potential difference of the 20 ohms resistor?

Answer 81

v=IR
= 0.06*20
= 1.3V

Question 82

Col elec pp q1d
(circuit: 4v power supply, 20 ohm and 40 ohm resistor placed in series)
(d) Fred argues that, since the 40Ω resistor is bigger it must have more current flowing
through it. Eric disagrees and says it must have a greater voltage. Who is correct and
why?

Answer 82

Current is the same in a series circuit.
There will be a larger pd across 40 ohm resistor v=IR
if I constant, greater R causes greater V.

Question 83

are lamps ohmic or non-ohmic?

Answer 83

Non-ohmic

Question 84

Why is it more accurate if measure both voltage and current (with 2 separate devices) when we only want to know the current?

Answer 84

It is more accurate because we now have an accurate measure of voltage while previously we assumed that the voltage of the power supply is accurate.

Question 85

Why would we blow a fuse if we placed an ammeter in parallel with a resistor?

Answer 85

• offered a bypass pathway for current that has less resistance
• resulting in a surge of current passing through the circuit that exceeds the safe operating limit of circuit components
• fuse will blow or the circuit breaker will trip, disconnecting the circuit to prevent damage to the components and prevent fire hazards.

Question 86

What forms a battery?

Answer 86

A series of cells.

Question 87

what to say when a light bulb is non-ohmic?

Answer 87

Resistance increases with increased current.

Question 88

The collision between the two carriages is inelastic. Explain the meaning of this term.
Previous parts mention momentum.

Answer 88

• conserve momentum but do not conserve energy of motion
• some Ek lost- turned into heat/ sound energy

Question 89

why’s it non-ohmic?

Answer 89

resistance is not proportional to voltage.

Question 90

The charged girl touches her brother’s ear. Both receive a mild electric shock. Explain.

Answer 90

Girl has negative electrical charge while neutral brother is relatively positive. Therefore charge will flow towards brother. They will feel a ‘spark’ as current passes.

Question 91

tasc 2017 pp q7a
A solar panel was installed on top of a house in order to run a water pump that filled a water tank on top of a nearby hill from the dam near the house.

Outline the energy changes that are occurring when the tank is filling with water. (2 marks)

Answer 91

nuclear (sun)-> light-> electrical energy-> kinetic energy-> gravitational potential energy

Question 92

Three resistors are connected to a battery in a laboratory experiment forming a series circuit. The total resistance is 131 ohms. Resistors are each 83, 16, and 32 ohms. Voltage= 8.5.

Calculate the current flowing through the 16 ohm resistor.

Answer 92

8.5/131= 0.065A

Question 93

Two resistors are connected to a battery in a laboratory experiment forming a parallel circuit. The total resistance is 11 ohms. Resistors are each 16 and 32 ohms. Voltage= 8.5.

Calculate the current flowing through the 16 ohm resistor.

Answer 93

v=IR
8.5 = 16 * I
I= 0.53 A

Question 94

Discuss the energy changes that occur when a solar-powered electric car accelerates up a ramp. (3 marks)

Answer 94

solar (em)-> electrical energy-> Ek(accelerating) /Egpe(higher) /Eheat (friction+air resistance)

Question 95

A piece of clay is thrown against a wall and sticks to it. Fred says that this is proof that the law of conservation of energy is false. Comment. (2 marks)

Answer 95

Fred initially had Ek. This is converted to:
1. increased heat of ball
2. increased heat of wall
3. sound energy
4. clay deformed

Question 96

What happens to the resistance of a non-ohmic device as the current flowing through it increases from 0.1 A to 0.5 A.?

Answer 96

R= slope of graph
Slope increases as I increases, therefore R increases