Differences between Theoretical and Experimental Emf (1 Viewer)
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leehuan
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Not enough info. Need a method.
Generally:
1. Theoretical values depend on the standard conditions (room temperature 25degC and standard pressure 1atm)
2. Materials are subject to corrosion
3. Concentration of the electrolyte may not be 1M
Generally:
1. Theoretical values depend on the standard conditions (room temperature 25degC and standard pressure 1atm)
2. Materials are subject to corrosion
3. Concentration of the electrolyte may not be 1M
RachelGreen
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Yeah like above, the experiment may have not been conducted under standard conditions 1M electrolyte concentration, 25 degrees celsius, and 1atm pressures).
However, I'm still unsure whether this reason is valid: Voltmeter while measures voltage, also uses current, and hence changes the potential difference (theoretically, you don't take into account the voltmeter's load since the current it uses is so small that it's negligible)
I got marked down in my pre exam test for writing "materials are subjected to corrosion" because my teacher told me it was my job to get rid of any oxide layers by sanding it down. Likewise with using reasons such as "voltmeter was faulty"
However, I'm still unsure whether this reason is valid: Voltmeter while measures voltage, also uses current, and hence changes the potential difference (theoretically, you don't take into account the voltmeter's load since the current it uses is so small that it's negligible)
I got marked down in my pre exam test for writing "materials are subjected to corrosion" because my teacher told me it was my job to get rid of any oxide layers by sanding it down. Likewise with using reasons such as "voltmeter was faulty"
leehuan
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Hence why I say method. If in the method sanding the metal was included then corrosion is obviously an excuse which won't get you a mark. Otherwise, your teacher was being harsh.
Faulty voltmeter is improper equipment - you never addressed validity at all if you used faulty equipment.
On the note of that other reason though...
Preliminary physics explains the purpose of the ammeter and the voltmeter
Ammeter - Measures the current at a specific point in the circuit. In order to effectively measure the current, it must have low resistance and effectively be placed in series with the circuit for accurate results.
Voltmeter - Measures the potential difference (work done to move each unit of charge) of an entire circuit. Ideally, because we're trying to measure a value for energy per charge, on the contrary you would want to connect the voltmeter in parallel to the circuit (so that it doesn't have to tamper with anything else), and also effectively increase it's resistance appreciably (so that essentially only negligible amounts of current is ever diverted into a voltmeter)
Faulty voltmeter is improper equipment - you never addressed validity at all if you used faulty equipment.
On the note of that other reason though...
Preliminary physics explains the purpose of the ammeter and the voltmeter
Ammeter - Measures the current at a specific point in the circuit. In order to effectively measure the current, it must have low resistance and effectively be placed in series with the circuit for accurate results.
Voltmeter - Measures the potential difference (work done to move each unit of charge) of an entire circuit. Ideally, because we're trying to measure a value for energy per charge, on the contrary you would want to connect the voltmeter in parallel to the circuit (so that it doesn't have to tamper with anything else), and also effectively increase it's resistance appreciably (so that essentially only negligible amounts of current is ever diverted into a voltmeter)