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

How the resistance of an ammeter changed when introduced into a circuit.

Extracts from this document...

Introduction

DC MEASUREMENTS

The experiment was to find out how the resistance of both an ammeter and voltmeter, using both an ammeter and voltmeter changed when introduced into a circuit. From doing this it was found that the resistance of the ammeter decreases as both the emf and current decrease, however the avometer suggested that internal resistance increases with the voltage.

Introduction

Voltmeter’s and ammeter’s use a moving coil galvanometer to take the current and a mechanical pointer to display the current. When using analogue components an important factor to consider is full-scale deflection, which is when the maximum deflection of an analogue instrument such as a moving coil meter is reached. At present the full-scale deflection of most instruments is 10-50 μA, but to overcome this shunting resistors are placed in parallel to carry the excess current.

...read more.

Middle

E was increased to 1v, which was measured by the digital voltmeter. The current I was recorded and compared to the expected value of 100μA. Then using the following formula,image03.png, Ra was calculated, and then the experiment was repeated with E=0.1v, range 50μ A and 10v, range 1mA.

Results

These results were taken using the avometer, and the intention was to find Rm, from the results.

Range (V)

Max E (V)

E/2

Rm (Ω)

3.0

3.0

1.5

60x103

10

10

5

20x104

30

30

15

60x104

...read more.

Conclusion

When using the digital voltmeter it has an error of ±1 digit. Whereas the avometer is a moving needle, which means the error is much greater as the needle can seem in two different positions from different angles.

Conclusion

In conclusion it was found that the resistances for both the ammeter and voltmeter behave differently, with the ammeter decreasing as the range is increased and the voltmeter increasing with range.

image06.png

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

    To check the accuracy of the ammeter and voltmeter, it will be checked that they both read zero when no current is flowing. If it does not, then the faulty equipment will be replaced. Once the results are recorded, they will be repeated to check if they are similar values.

  2. Find The Internal Resistance Of A Power Supply

    take the voltage and ammeter reading and then switching it off again to let it cool. The load resistance will be increased uniformly by moving the contact in the potentiometer across 2cm seven times and therefore current readings will decrease.

  1. eletrical dc motors

    this is called mutual induction. By adding a load to the secondary circuit, one can make current flow in the transformer, thus transferring energy from one circuit to the other. In an ideal transformer, the induced voltage in the secondary winding is a fraction of the primary voltage and is

  2. The potato - a source of EMF

    I also predict that the EMF of the potato will decrease as more and more of the chemicals inside of the potato are being used up over the duration of the experiment; by the time the 3rd set of readings have been taken the potato cell will have reacted with

  1. Coursework To Find The Internal Resistance Of A PowerSupply

    E - Ir V = -Ir + E y = mx + c Therefore the gradient (m) is the internal resistance,-r, and the y-intercept is the Electromotive Force (E). Safety Precautions: As we are using mains electricity, we must make sure that no water should come in contact with the

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

    The ammeter is connected in series with the resistor and is not included in the parallel connection. In these predictions I will be picking different resistances for the variable resistor, and then trying to calculate the resistance using the meter readings.

  1. Practical Project (2863/02): The Characteristics of a Shunt Wound Motor

    The Newton meters are then attached to a bar on a retort stand to allow the tension to be altered. A similar leather strap would be placed on the opposite side of the motor, as shown in the diagram on the right, which shares the tension across the straps and

  2. Observe and record the brightness, voltage difference (the potential difference between two points in ...

    I predict that the more amounts of bulbs you have in a circuit, the dimmer they will be, and this also follow for the parallel circuit. Also, the higher the voltage in the cell, the more energy it gives to the electrons pushed out.

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