c6 Flashcards
1
Q
Why do metals, soluble salts, and water conduct easily?
A
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
2
Q
Why are some substances a good insulator? Give an example.
A
Glass is an insulator because any free electrons or ions cannot flow within the glass.
more e.gs: plastic
3
Q
What do we refer as conductors?
A
We generally refer to substances as conductors or insulators at low voltages. (anything can conduct at high voltages or the distance is small enough)
4
Q
What are sparks and lighting?
A
light given off when air is made to conduct.
5
Q
cell
A
a device that contains two substances with different electron affinities
6
Q
separation of charges=?
A
potential electrical energy
charges flow, energy follows when positive is connected to the negative side
7
Q
battery
A
stack of cells
8
Q
current electricity
A
the study of moving electrical charges, and the transfer and transformation of energy
9
Q
early type cell
A
zinc carbon
10
Q
two main characteristics of batteries
A
- 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
11
Q
forces on the electrons at each stage that prevents them from flowing
A
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)
12
Q
forces on the electrons at each stage that allows them to flow
A
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
13
Q
conventional current
A
we pretend that imaginary positive charges flow in the opposite direction (the non pretended one is the electron flow
14
Q
current
A
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
15
Q
charge
A
- property of a body
- symbol q or Q
16
Q
Amp
A
1 coulomb of charge flow past per second
17
Q
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)
A
Ek= 340357 + 200781= 541139
= 5.41 *10^5 J
18
Q
Discuss the energy changes in each of the following situations:
(a) A petrol engine car is accelerating up a hill.
(2 marks)
A
Potential chemical energy converted to
1. Ek (car accelerating)
2. E GPE (car increasing height)
3. Heat (friction and air resistance)
19
Q
Discuss the energy changes in each of the following situations:
A skydiver falling at terminal velocity (2 marks)
A
v constant-> no increase in Ek
E GPE converted to heat (air resistance)
20
Q
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)
A
Work done on the bag:
w= mgh same
greater
same
Power input to bag:
p= w/2t less
greater
same
21
Q
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
A
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
22
Q
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)
A
- 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.
23
Q
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)
A
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
24
Q
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)
A
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
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)
P before= mb= (70.0 + 53.9) *5.0= 619.5 kgms^-1
P after= MsVs + MoVo= 2.0*70.0+ Vo*53.9
P conserved
therefore 619.5= 140+ 53.9 Vo
therefore Vo= 8.896
= 8.9 ms^-1 west
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.
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
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)
Ep = mgh
Ep = 1.8 x 109 x 9.81 x 180
Ep = 3.2 x 1012 J (2 s.f.)
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)
P = ΔE/t
P = 1.43 x 10^12/ 24 x 60 x 60
P = 1.7 x 107 W (2 s.f)
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)
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’.
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:
diagram ans in photos
i V = 1.5 V
ii I = 𝑉/𝐼 = 1.5/ 6.0 = 0.25 A
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)
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)
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)
Non-ohmic resistors do not have a constant
resistance at all applied voltages.
On the graph this is indicated as a non-linear graph.
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.
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.)
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.
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
35
Why is it necessary for the vaulter to have quite a long run-up?
To gain Ek to turn into Ep (elastic) in pole later.
36
c Describe the role the pole plays in the energy conversion processes in pole vaulting.
(c) EK to convert to elastic Ep for the pole so that upwards EK can be achieved.
37
What is the source of the energy that re-models the front of the car and scatters stones in all
directions.
EK -> work done on stones
38
Work is defined in physics as...
1. Change in energy of a body
2. Force applied multipled by the displacement in the direction of the vector of the force
39
Work is usually defined ______ a force. Give an example as well.
Against. E.g. lifting an object is working against gravity
40
A closed system is...
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.
41
What is the principle of conservation of energy?
Energy is neither created nor destroyed.
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?
4850j
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
b
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.
No.
As Ek is not conserved.
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.
Ek = ½mv2
Ek = ½ x (98 + 84) x 0.222
Ek = 4.4 J
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)
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.)
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)
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.
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)
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
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.
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.
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)
Δ Ek= 1/2mv^2 - 1/2mu^2
= 1/2 * 92 (3.00^2- 6.00^2)
= -1242J (-1.24 kJ)
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
Total work done by cyclist= (ΔEp + Δ Ek + WF)
= 1173- 1242+670)J
= 601 J
P=W/t= 601/8.00 = 75.1 watts
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)
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.
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?
Pbefore= Psuv +Pcar= 2560 * 105 + 1040 (-89)= 176240
Pafter= 3600v
v= 48.95
= 49 ms^-1
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)
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.
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)
W= Fdrag x 5 = 7.727 x 25 = 193 = 190 J
Cos 15= Fdrag/8.0
Fdrag= 8.0 cos 15
= 7.727
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)
Ek = (½ x 98 x 3.72) + (½ x 84 x 4.82)
Ek = 1638 J
Ek = 1600 J (2 s.f.)
57
How many volts do powerpoints give out?
240v
58
When a man jumps ashore from a boat, the boat is simultaneously driven away from the
bank.
(a) How is this explained?
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.
59
Use the Law of Conservation of Momentum to explain why
(a) an astronaut moves backwards when throwing a hammer in space.
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.
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.
- 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.
61
Work is done when a force causes an object to ______
undergo displacement
62
Energy of a body determines its ability to ______
do work
63
The amount of potential energy the object possesses is equal to ____
the work done in lifting the object to that level.
64
work is ______ of energy.
elaborate.
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.
65
What is inelastic energy?
A collision which loses mechanical energy as heat or sound.
66
What is power?
Rate of doing work.
67
What is current electricity?
The flow of free electric charges through a conductor.
68
Is charge a fundamental or derived quantity?
Derived. Because it's calculated with I*T
69
What is current? Is it fundamental or derived?
rate of flow of electrical charge. fundamental because it doesn't derive from other base quantities.
70
What does an ammeter do?
Measures the current passing through a point in an electrical current.
71
Is electric charge ever used up?
No. As electrons do not disappear, energy is used up however.
72
What does emf tell us?
how much energy is given to each coulomb of charge delivered by the battery.
73
What direction does electric current flow out from a battery?
From the positive terminal (longer line in a battery), in towards the negative.
74
Electric current flows from a region of ____ to a region of _____. What is this difference called?
High energy to low energy. Potential difference, aka. voltage.
75
A potential difference of 6 volts between two points means...
each coulomb of charge will lose or dissipate 6 joules of energy as it moves between the points, which becomes heat energy or similar.
76
What does a voltmeter measure?
The difference in electrical energy between two points in the circuit- potential difference. (usually before and after a resistor or other component)
77
What's the difference in current transmission in a series connection and in a parallel connection?
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).
78
Why's the difference between the location of where an ammeter and a voltmeter are connected in a circuit?
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.
79
What is the maximum safe amount of current and what's the fatal amount?
1 mA
100 mA
80
What's the difference between ohmic and non-ohmic conductors?
ohmic: linear relationship, resistance remains constant as voltage varies
non-ohmic: non-linear relationship, resistance changes as the voltage varies
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?
v=IR
= 0.06*20
= 1.3V
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?
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.
83
are lamps ohmic or non-ohmic?
Non-ohmic
84
Why is it more accurate if measure both voltage and current (with 2 separate devices) when we only want to know the current?
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.
85
Why would we blow a fuse if we placed an ammeter in parallel with a resistor?
- 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.
86
What forms a battery?
A series of cells.
87
what to say when a light bulb is non-ohmic?
Resistance increases with increased current.
88
The collision between the two carriages is inelastic. Explain the meaning of this term.
Previous parts mention momentum.
- conserve momentum but do not conserve energy of motion
- some Ek lost- turned into heat/ sound energy
89
why's it non-ohmic?
resistance is not proportional to voltage.
90
The charged girl touches her brother's ear. Both receive a mild electric shock. Explain.
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.
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)
nuclear (sun)-> light-> electrical energy-> kinetic energy-> gravitational potential energy
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.
8.5/131= 0.065A
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.
v=IR
8.5 = 16 * I
I= 0.53 A
94
Discuss the energy changes that occur when a solar-powered electric car accelerates up a ramp. (3 marks)
solar (em)-> electrical energy-> Ek(accelerating) /Egpe(higher) /Eheat (friction+air resistance)
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)
Fred initially had Ek. This is converted to:
1. increased heat of ball
2. increased heat of wall
3. sound energy
4. clay deformed
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.?
R= slope of graph
Slope increases as I increases, therefore R increases
