Careful Way of measuring of Emf and or Inner Resistance of a Cell Dissertation

Careful measurement of emf and or internal amount of resistance of a cellular Aim

To measure volt quality and current in the routine and from that figure lift weights emf and internal resistance of the cellular, to identify problems involved and deal with these people in the most effective way and maintain a safe working environment all the time. Background

EMF (electromotive force) is a way of measuring work done per unit of charge which is measured in volts. Inner resistance is usually resistance in ohms from the cell. I will be using a 1 ) 5V battery pack in the try things out. I will measure the voltage and current applying multimeters. Calculation method

I actually intend to piece together the formula ‘ε=Ir+IR' to create ‘V= -Ir +ε' then draw the y=mx+c graph equation to find EMF and internal resistanc`e. The sumado a axis intercept measures EMF and the lean gives you internal resistance. Projected main causes of error

The multimeter has some inaccuracies: Resistance is accurate to 0. 1 ohms (+/-0. 8%), Current is accurate to 0. goal A (+/- 2%) and voltage can be accurate to 1 mV (+/- 0. 5%). These by themselves are slight problems although may have a total affect. The resistance of all wires joined up with together is usually 0. six ohms. Nevertheless the biggest concern after early testing may be the fluctuations around the ammeter, the ammeter very rarely settles on the value which leads to an inaccuracy of zero. 02 v (+/- zero. 01 volts) and 0. 02 amps (+/- 0. 01 amps). This doubt could be very high especially with reduced values 1st experiment

We started using a simple experiment to obtain figures that improvements could be achieved.

This is the outlet diagram of my first experiment

It absolutely was soon very clear that the adjustable resistor didn't have the necessary resistance to generate the current necessary for the try things out. I changed the original adjustable resistor having a rheostat because the level of resistance could be altered in a more thready way rather than with the dramatical increases in the variable resistor. There are handful of safety risks in my test but to be sure I ensured there was simply no copper showing in wires, only touched the rheostat when it wasn't connected to the cellular and was wary of problems associated with getting near other experiments.

Current (A)| Concern (A)| Volts (V)| Doubt (V)| 0. 23 | +/- zero. 01| 1 . 439| +/- 0. 01

0. twenty nine | +/- 0. 01| 1 . 425| +/- 0. 01

0. 31| +/- 0. 01| 1 . 421| +/- zero. 01

0. 33| +/- 0. 01| 1 . 415| +/- 0. 01

zero. 36| +/- 0. 01| 1 . 408| +/- 0. 01

0. 41| +/- 0. 01| 1 . 398| +/- zero. 01

zero. 45| +/- 0. 01| 1 . 388| +/- 0. 01

0. 52| +/- 0. 01| 1 . 372| +/- zero. 01

zero. 58| +/- 0. 01| 1 . 359| +/- zero. 01

0. 68| +/- 0. 01| 1 . 339| +/- 0. 01

0. 78| +/- 0. 01| 1 . 317| +/- 0. 01

zero. 91| +/- 0. 01| 1 . 299| +/- zero. 01

My own initial benefits and chart (on following page):

My personal initial results were very motivating as the correlation was very strong. My spouse and i repeated a similar experiment although taking more hours.

These benefits form a negative relationship. However towards the end of the try things out, the benefits went away in the line of best suit sharply demonstrating there was a mistake that clearly occurred throughout the experiment. My spouse and i originally believed this was a problem with the power supply heating up over time so chose to measure resistance of rheostat in my up coming experiment hence the battery could have a time to cool down. Current (A)| Doubt (A)| Voltage (V)| Doubt (V)| 0. 74| +/- 0. 1| 1 . 286| +/- 0. 1

zero. 48| +/- 0. 1| 1 . 354| +/- 0. 1

zero. 36| +/- 0. 1| 1 . 375| +/- 0. 1

zero. 29| +/- 0. 1| 1 . 396| +/- zero. 1

0. 23| +/- 0. 1| 1 . 400| +/- 0. 1

zero. 20| +/- 0. 1| 1 . 392| +/- 0. 1

Discover atatched chart (next page)

I also measured the voltage by my battery in between tests and found out my ‘1. 5V' electric battery to be making 1 . 559V, a percentage mistake of 4%. To try and rectify this problem We tried new batteries right up until one which has a very low percentage error was found, one with 1 ) 503V which had negligible error.

Second experiment

Since my preliminary first try things out brought back...



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