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

# To find out what happens to the efficiency of a motor as I change the mass it lifts.

Extracts from this document...

Introduction

Coursework – Energy

Aim: To find out what happens to the efficiency of a motor as I change the mass it lifts.

METHOD

When devices transfer energy, only part of it is USEFULLY TRANSFERRED to where it is wanted and in the form that it is wanted. The rest is transferred in some non-useful way and therefore it is ‘wasted’. The ‘wasted’ energy and the ‘useful’ energy are both eventually transferred to the surroundings. The greater the proportion of energy supplied to a device, THAT IS USEFULLY TRANSFERRED, the more efficient we say the device is.

A motor is a device that transfers electrical energy into rotational kinetic energy, which can be used to lift a load. We are going to try and find out how the efficiency of a motor differs as we change the mass that it is required to lift. To do this we will let a small electric motor lift a small load 0.5m off the ground and work out it’s efficiency, increasing the weight of the load it has to lift by 0.1N each time we run it. Below is a diagram showing how the circuit for this experiment will be set up:

As you can see, the motor has to be connected to the ammeter, voltmeter and the power supply. The ammeter is placed in series and the voltmeter is placed in parallel. The motor should be clamped tightly onto a stand over one metre off the ground. A piece of string capable of reaching to the floor should be attached to the spindle of the motor, whilst the other end should be attached to the mass hook.

When the experiment is run, a stopwatch should begin timing as the power supply is switched on.

Middle

Energy has to be transferred from one form to another, e.g. a hairdryer turns electrical energy from a mains supply into movement energy (the fan), heat energy (to heat the air as it passes through) and sound energy (waste energy). You cannot create it or destroy it. Energy efficiency is how much of the energy you put into an appliance or machine is transferred into the useful energy that you are trying to get out. All machines in the real world have an efficiency that is less than 1 (or 100%). In the case of the motor above, part of the electrical energy put in is transferred into the useful movement energy, however, the machine also transfers it’s energy into two other waste forms: it creates a little heat and a little sound, caused by the force of friction on it’s moving parts, as in all machines. The greater the proportion of energy supplied to a device, that is usefully transferred, the more efficient the device.

To calculate the efficiency of any device we need to use to the following formula:

EFFICIENCY = USEFUL ENERGY TRANSFERRED BY DEVICE

TOTAL ENERGY SUPPLIED TO DEVICE

… So in the case of an appliance that coverts 200 joules of electrical energy per second into 150 joules/sec of waste heat energy, 20 joules/sec of useful light energy and 30 joules/sec useful sound energy… EFFICIENCY = 50 ÷ 200 [× 100] = 25%

We are trying to find out how the efficiency of a motor changes as we increase the mass it has to lift, so we need to remember that the efficiency of a motor is determined by how much of the electrical energy put in is transferred into useful energy output. The useful energy output is gravitational potential energy (GPE).

Conclusion

there would be no useful energy being transferred, all electrical energy inputted would be transferred into non-useful waste forms. It would have been interesting to find out what this weight is. My graph displays a line of best fit which makes it difficult to predict how it will continue. It is very hard to tell from my data whether the line should slope downwards in a straight line, or decrease slowly at first, then more quickly, etc. Therefore collecting more data would provide me with more informative results.

Carrying out further tests around 0.6N – the apparent optimum weight

It would be interesting to try and find out exactly where my line of best fit should peak, and what the precise optimum weight for the efficiency of this motor is. By collecting further, accurate results I could determine what weight this motor will lift most efficiently, e.g. 0.62N.

By plotting more points around the area where my line of best fit peaks on my graph, I would be able to tell exactly how my line of best fit should be shaped around it’s peak.

Lifting the loads higher and finding out at what point is a motor most efficient

We could try and find out how much a motor’s efficiency differs depending on how much of the way through a lift it is. For example, is a motor more efficient when it has just begun lifting it’s load, or when it is almost at its full height. We could do this by letting a motor lift a load slowly, whilst measuring the electrical energy input just after it starts to lift, and whilst it has been running for longer.

We could also try and determine whether a motor is on the whole more efficient when lifting to a small height or to a large height, or in other words, how does the length of time it has to lift a load for affect a motor’s efficiency?

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism 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

# Related GCSE Electricity and Magnetism essays

1. ## &amp;quot;My aim is to find out how much energy is released when burning different ...

the most energy, but this is not true because of my anomalous results. My method could have been a bit better by being more accurate. If I was to do this again I would redo the Hula Hoops and Walker Lite to make sure they are completely accurate.

2. ## Design an experiment to predict and test the output from a simple AC generator.

Bulbs come in packs of 10 so the cost for a pack divided by 10 is the cost for one bulb. Bulb Resistance (?) Ideal Voltage (V) Ideal Power (W) cost per bulb 1 5.00 2.24 1.00 �0.435 2 7.50 2.74 1.00 �0.435 3 12.50 3.54 1.00 �0.435 4 23.33

1. ## Investigate how mass affects the diameter of an impact crater.

have caused the fine aquarium gravel particles to move, collide and rub against each other which would have caused the particles to travel a smaller distance due to the friction reducing its velocity. * Energy transferred to compress the surface - as mentioned above, great effort was taken to ensure

2. ## Physics Coursework Gravity Investigation

For example, parts of the tennis ball may have been worn away, an unequal quality of surface causing it to bounce irregularly. The tennis ball also has a white seam, which may have been the part of the ball that made contact with the floor, resulting in another irregular reading.

1. ## Find the realtionship between gravitational potential and kinetic energy

Increase in height of ramp=increase in velocity of trolley Equations/Units/Ranges to be used Range: To make this investigation successful, a sensible range must be chosen and also the amount of readings to record in order to come up with a useful and informative outcome.

2. ## How does the Relative Molecular Mass change in heat combustion of an alcohol?

Reweigh the burner and its contents to measure the loss of fuel during combustion. I will repeat this process for all the alcohols: methanol, ethanol, propan-1-ol, butan-1-ol and pentan-1-ol. For safety reasons I will wear goggles throughout the experiment, to prevent any hot substances spitting into my eyes.

1. ## The Efficiency of an Electric Motor.

By reducing the torque the motor can lift a wider range of weights. I have tried to reduce the friction in the pulleys by oiling them. 2. The radius of the cotton reel used to wind the string around the motor shaft increases as more string is wrapped round it.

2. ## Investigating The Heat Of Combustion Of Alcohols.

This is to ensure that as little heat energy as possible is lost or not used to heat the can. This also ensures that all the alcohols have equal distance from the copper calorimeter so the same amount of heat energy is lost to the surroundings.

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