Question

electrical resistance

1. The high-resistance paper has a resistivity of 1:25 Ωm. How do your values compare? What
are possible causes for discrepancies between the known value and your calculated values?

Resistivity measurements

	Measured resistance	Length	Width	Cross-sectional area	Resistivity
	(Ω)	(m)	(m)	(m2)	(Ω·m)
1	18.6	.052	.015	.00078	.000134
2	17.5	.076	.02	.00152	.001151
3	52.	.10	.01	.001	.001300
4
5
6

** thickness = .25 mm

2. What are possible causes for discrepancies between theoretical and measured values of resistors in series and in parallel?

3. When it is practical to connect resistances in series and when in parallel?

Answer 1

1. The possible reasons of discrepancies between the theoretical and measured values of resistances are-

• Temperature, as temperature increases, resistivity increases
• Humidity
• Instrument calibration
• Error while measuring

2.

The possible reasons of discrepancies between the theoretical and measured values of resistances in series and parallel are same as that of other resistances(explained above) as well as the resistance of the connecting wires gets added to final resistance thereby causing the discrepancy.

3. Connecting in series is practical when-

• In a circuit when you want all the devices to get switched and switched off at the same time. Example- in a circuit we can connect a LED power indicator in series to make sure the current is flowing through the circuit

Connecting in parallel is practical when-

• Lighting in the house, you don't want all your appliances working at the same time. If one of them gets burned, the other devices will still work.