Resistance experiments

Question 1

3 practicals for this?

Answer 1

1. Investigation of the IV Characteristics of the Filament of a Lamp and Metal Wire at Constant Temperature
2. Investigation of the Variation of Resistance with Temperature for Metal Wire
3. Determination of the Resistivity of a Metal wire

Question 2

Elaborate 1.
(General, not blurted)

Answer 2

• Ohm’s law states that for a conductor,
• the current (I) is ∝ to potential difference (V)
• provided physical factors such as temp. & pressure
• remain constant.
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• ∴, plotting I-V characteristic,
• of a metal wire and a filament lamp,
• the validity of Ohm’s law,
• as applicable to each of these components, can be determined
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• Graph of I against V is linear for metal wire
• and non-linear for a filament of a lamp

Question 3

Elaborate 2.
(Also general, not blurted)

Answer 3

• Resistance increases w/ temperature
• for metals in a linear relationship
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• Practical will enable data to be obtained
• to investigate this relationship
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• Water bath used to heat a coil (in boiling tube in oil)
• to a range of temperatures from
• 0° - 100°C w/ ohmmeter to measure resistance
  O_o
• Repeat experiment during cooling
• Graph: resistance against temperature
• Straight line through origin (∝)

Question 4

Elaborate 3.
(Still general, not blurted at all)

Answer 4

• Resistivity (ρ) found using eqn:
• R = ρ(l/a)… also knowing what each symbol means…
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• Can be compared w/ equation for a straight line y = mx + c
• Graph: R against I, straight line through origin
• Gradient: ρ/A
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• Cross-sectional area found using A = πr²
• Resistivity calculated by ρ = gradient x A

Question 5

Consider “fore-shortening”

Answer 5

,’:)