• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month
  1. 1
  2. 2
  3. 3
  4. 4
  5. 5
  6. 6
  7. 7
  8. 8
  9. 9
  10. 10
  11. 11
  12. 12
  13. 13
  14. 14

The aim of the experiment is to verify the maximum power theorem and investigate the efficiency with which energy is transferred from a source of e.m.f to a load resistance.

Extracts from this document...


Experiment 8: Energy Transfer in a D.C. Circuit


    The aim of the experiment is to verify the maximum power theorem and investigate the efficiency with which energy is transferred from a source of e.m.f to a load resistance.

Experimental Design


Name of apparatus


Battery of three dry cells with added artificial internal resistance (30Ω)



Resistance box





With zero error (± 1 mA)


Connecting wires







Description of design:

    In this experiment, we will verify the maximum power theorem by using the above circuit. When we vary the resistance of the resistance box provided, the potential differences across the resistance box and internal resistor, hence current drawn from the dry cell also is varied, so the ammeter can measure the current flowing in the circuit at different equivalent resistance of the circuit.


    Friction is a very common and important force in our daily life. Although friction may disturb our motion, many movements of our human also need the help of the friction. For example, friction between our shoes and the ground helps us to walk and the friction between the wheels and the ground also helps the car to move. So friction is essential for the motions in our daily life.

    Friction always opposes the motion performed by any object. It forms when two surfaces are in contact. It increases as the other forces tending to produce the motion increase, however, it has its maximum value. When an object is in contact with a rough surface, friction is formed between the two contact surfaces. As the applied increases, the static friction also increases. When the applied force is equal to the maximum magnitude of the static friction, it will move.

...read more.


The kinetic friction: 1.2N ± 0.05 N

Coefficient of static friction = static friction / normal reaction force

                       = 1.4 / (0.194*10)

                       = 0.722 (Cor. to 3 sig. Fig.)

The uncertainty = 0.05/1.4 + 0.0005/0.194 = 0.0383 (Cor. to 3 sig. Fig.)

The percentage error = 0.0383 * 100% = 3.83%

So, the coefficient of static friction = 0.722 ± 0.0383

Coefficient of kinetic friction = kinetic friction / normal reaction force

                       = 1.2 / (0.194*10)

                       = 0.619 (Cor. to 3 sig. Fig.)

The uncertainty = 0.05/1.2 + 0.0005/0.194 = 0.0442 (Cor. to 3 sig. Fig.)

The percentage error = 0.0442 * 100% = 4.42%

So, the coefficient of kinetic friction = 0.619 ± 0.0442

Part B: Coefficient of friction for various masses


  1. All wooden blocks were weighed by the beam balance and labeled with numbers.
  2. The scale of the spring balance was set properly to zero.
  3. The sand paper was placed on the table.
  4. A wooden block was placed on the table.
  5. The wooden block was connected to the spring balance in series.
  6. The block was pulled until the block was moving.
  7. The reading of the static friction was recorded.
  8. The block was pulled to move in constant velocity.
  9. The reading of the kinetic friction also was recorded.
  10. Step 6 and 7 were repeated except increasing the numbers of the blocks that were held by the rubber band.


    In this experiment, we should keep the spring balance in horizontal position in order to ensure that only the applied force support the motion of the wooden block. If it is not in horizontal position, horizontal component of the applied force will support motion. Secondly, we should keep the wooden block that it is moving in constant velocity as much as possible; otherwise, the magnitudes of the applied force will be different from time to time. Moreover, the sand paper may make the wooden surface become smoother, and hence the static and kinetic friction may be different from the original one. So the numbers of pulling process should be minimized.

...read more.


   In part A, we can find out the relationship between the friction and the applied force. When the applied force increases, the static friction also increases and it is direct proportional to the applied force which can be seen from the graph. So it can balance the applied force to make the block remain at rest. However, when the applied force further increases and overcome the maximum limiting friction which is the peak of the graph. After reaching the limiting friction, the graph drops and levels off. It shows that the block obeys the Newton’s first law. The applied force is same as the kinetic friction but in opposite direction. From graph, it shows that the static friction is smaller than the kinetic friction.

   In part B, we can study the effect of normal reaction force on the static and kinetic friction and estimate the coefficient of static and kinetic friction from the graph, From the graph plotted, we can conclude that the normal reaction force is direct proportional to the static and kinetic friction from the graph. We also can estimate the coefficient of the static and kinetic friction by finding out the slope of the graphs. So the coefficients of static friction and the kinetic friction are 0.727 ± 0.033 and 0.574 ± 0.050 respectively.

    In part C, we study the effect of contact surface on the friction. From the experimental result, we can conclude that the size of the contact surface does not cause significant change to the kinetic friction. The difference between the ways of placing the blocks is caused by the experimental errors discussed above. However, we can further investigate how the nature of the contact surface affects the kinetic friction such the metal surface.


Wikipedia (Friction)


New Way Physics for advanced level Mechanics

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. In this experiment, we will measure the e.m.f. and the internal resistance of a ...

    6. The rheostat was changed into different values. 7. The corresponding readings of ammeter and voltmeter were recorded. 8. The data obtained was tabulated. Precautions To ensure the accurate and precise data is obtained, we should be aware of the following precautions: Firstly, the internal resistance of the dry cell is

  2. Single Phase Transformer (Experiment) Report.

    (So now instead of the ? being a value of zero, the cos ? now becomes the value 0.8 therefore the value for sin ? is 0.6,and due to it lagging then in the voltage regulation equation the sign in the middle must be an add and not a minus.)

  1. The potato - a source of EMF

    When there is no internal resistance at all. (V=IR, this is learnt as GCSE where it is assumed there is no internal resistance.) 2. When no current is flowing. The values for the equation above can be rearranged and substituted into the straight line equation as is shown below.

  2. Measuring the e.m.f. And Internal Resistance of a Cell

    standard I was trying to achieve and so can be taken as reliable since the techniques were accurate though not always suitable. The technique used to perform this experiment was sufficiently accurate for this investigation. However the suitability of the techniques was doubtful.

  1. The Resolving Power Of The Eye

    The sum of these errors is the total percentage error of the readings to 3sf. The anomalous result in the first set of readings is discounted from the averages taken. This result was caused by a change in light intensity during the reading and the pupil not being fully adjusted to the conditions i.e.

  2. To find the factors that affect the amount of E.M.F. being produced. The amount ...

    Green wire - attached to oscilloscope carrying the electro-motive-force to it to be measure. Planning Safety precaution * Electricity is dangerous therefore be careful while connecting the circuit by having the power supply turned off at start. * Wire striper is sharp therefore while stripping careful not to cut your hand.

  1. Energy Efficiency Experiments

    Voltage x Time Energy output = 0.8 x 9.81 x 1.45 = 11.38J Electrical energy → Kinetic energy + Heat energy → Gravitational potential energy + Heat energy Efficiency = 11.38 ÷ 24 x 100 = 47.42% C:\Users\Hello\Pictures\TPhoto_00011.jpg Method-Experiment 5 In this last experiment we poured 500ml of water and timed how fast it took to get to the bottom.

  2. Electrical Energy Questions and Answers

    The field lines do not cross each other 1. Describe electric potential different (voltage) between two points as the change in potential energy per unit charge moving from one point to the other (joules/coulomb or volts) 1. In order to move the charges, energy is required.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work