• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Internal resistance of cells.

Extracts from this document...

Introduction

Internal resistance of cells. Plan: Introduction: A toy manufacturing company has received complaints about a battery driven toy car. Apparently after only a few hours use the toy car's batteries need replacing. The customers are unsatisfied with the toy car and want their money back, the toy company believes that the short life span of the battery is not down to the toy car being faulty but that modern batteries have a high internal resistance, which causes poor performance. It is our job to see if this in fact the case. The internal resistance of a battery can be related to the current, resistance of an external load and emf (electromotive force) by Ohms law: Where IR is the terminal pd and Ir is the pd across the internal resistance, by also considering the equation V = IR we can substitute this in to produce: With this equation we can arrange it in The form y = mx + c, In this form the internal resistance (r) becomes the gradient and the emf (E) is the y axis intercept. So by producing a simple circuit and measuring values for x and y, e.g. y = the voltage across the external load and x = the current we can produce a graph that will give an accurate value for the emf, and more importantly, the internal resistance of the battery. ...read more.

Middle

readings that are too complicated to work with and feel that due to time I would work better with only 2d.p readings. The variable that I will keep constant is the exact battery I use for my results, so if I have to repeat any anomalous results the battery will still have the same internal resistance. To check the accuracy of my readings I can calculate the current and voltage using the equation V = IR. Therefore by considering the sensitivity of the equipment I can work out maximums and minimums if I need to. This may help if the readings for the current become very small and will help improve my accuracy when plotting a graph. Results: By collecting this data and using the equation V = rI - E I can plot a graph where the gradient will be the internal resistance and the y intercept will be the emf, and with these results I will be able to tell if the battery obeys Ohms law and prove if modern batteries have a high internal resistance which could lead to poor performance or not. Alkali Battery: Resistance (?) Current (I) Voltage (V) Current (I) Voltage (V) 1 0.94 1.07 1.070 0.94 3.3 0.38 1.36 0.412 1.254 10 0.13 1.50 0.150 1.30 12 0.13 1.51 0.126 1.56 15 0.10 1.53 0.102 1.50 22 0.07 1.55 0.070 1.54 33 0.05 1.56 0.047 1.65 47 0.03 1.57 0.033 1.41 56 0.03 1.58 0.028 1.68 ...read more.

Conclusion

Using what I found out and comparing to others in the group the results show me that the internal resistance of a modern (alkali) battery is smaller than that of the other. This leads me to the conclusion that the modern batteries don't have a higher internal resistance and that the performance of the toy car cannot be blamed on this. Internal resistance is due to the material that the battery is made from, the internal resistance of any power supply cannot be removed but it can be measured. When there is a current flowing through both r and R, energy is transferred in the internal resistance (r) of the battery as it gets warm, and also in the external load (R). This means that the terminal p.d. (the p.d. across R, the external load) is less than the full emf of the battery. So if the battery has a high internal resistance then less power is transferred to the circuit. In this case the resistance of the external load is fixed, i.e. the toy car, and the current depends on the internal resistance of the battery. So if the battery has a high internal resistance then a smaller voltage will flow, if the toy car has a small resistance the power of the battery will be drained very quickly and this may be the problem in this case. Rachel Jeffreys ...read more.

The above preview is unformatted text

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 ...

    Secondly, the set-up of the experiment is used for long time or the switch is plugged on for a long time, it will produce heat to the set-up and then the resistance of the set-up will increase. As a result, the calculated internal resistance of the dry cell will be

  2. Investigating the E.m.f and Internal Resistance of 2 cells on different circuit Structures.

    have half the values of the series with two cells, because it is the same circuit but with half of the number of cells so internal resistance and e.m.f should be exactly half of the series circuit with two cells e.m.f = Ir + IR = (0.25*12)

  1. Investigate methods of finding and comparing the e.m.f and internal resistance of different cells ...

    should have been used to gather more efficient results. A second power supply could be used to compare the values of e.m.f and internal resistance. This could be the second set of p.d values and may give a more accurate result.

  2. Design and Carry Out an experiment to determine the EMF and Internal Resistance of ...

    5.32 2 2.66 0.55 6.42 5.32 By taking the gradients from the different graphs I have attained the following results for internal resistance and e.m.f. Power Supply Readout E.M.F Difference Internal Resistance 4V 4.1v 0.1 0.46 5V 5.1v 0.1 0.39 6V 6.3v 0.3 0.55 CONCLUSION Looking at my results, I

  1. The potato - a source of EMF

    leads Join components in the circuit Variable resistor Change the load resistance Voltmeter Record the p.d. (Volts) Ammeter Record the current (Amps) Ohmmeter accurately measure the resistance on the variable resister Measuring tape Measure the distances between electrodes (8cm, 4cm, 2cm)

  2. The aim of the experiment is to verify the maximum power theorem and investigate ...

    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.

  1. To find which of the circuits, shown below, are most suitable to measure a ...

    from the ammeter. As shown in the above equation you are multiplying by the current and then diving by that same current to give the answer, and thus this cancels down to give the resistance. Other Values obtained due to calculations: Circuit Two Value specified on Resistor (?)

  2. To find out the internal resistance and EMF of a given power supply

    and r is the internal resistance (?)) we could find out what the gradient of the V/I graph plotted would represent. Since V here is plotted on the y-axis, and I is plotted on the x-axis, we can arrange the equation into the following form: V = - Ir +

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