20-6-2023

#physics#prac

1. What does your graph indicate about the relationship between potential difference and current for the wire? State the relationship in mathematical form. The graph for the light bulb indicates that as current increases at a constant rate, potential difference increases at an increasing rate, following a parabolic relationship of $V=15120\times I+88.638\times I-0.0727$. $\therefore$ The light bulb is non-ohmic.

   Meanwhile, the fixed resistor indicates a direct proportionality, where an increase in current at a constant rate results in the potential difference increasing at a constant rate, following the linear relationship of $V=10.63\times I-0.042$. $\therefore$ The fixed resistor is ohmic.

2. Is the resistance constant for each component? No, the resistance is not constant for the light bulb, but was constant for the fixed resistor. This is demonstrated by calculating the resistance for each date points using the rule $R=\frac{V}{I}$. Light Bulb:

   • For $V=1.7$ and $I=0.009$, $R=118.89\text{ohm}$
   • For $V=3.4$ and $I=0.0127$, $R=267.72\text{ohm}$
   • Evidently these two values are not very similar, so not a constant resistance. Fixed Resistor:
   • For $V=2$ and $I=0.2$, $R=10\text{ohm}$
   • For $V=3.47$ and $I=0.33$, $R=10.52\text{ohm}$
   • Evidently these two values are relatively close, so there is a constant resistance.

3. The unit of resistance is OHM. Sow what 1 ohm is equal to in terms of volts and ampere. $R=\frac{V}{I}\therefore$ If V = 1 and A = 1, R will = 1.

4. An ohmic component is one for which the resistance is constant, at any voltage. Are these components ohmic? Justify your answer. The fixed resistor is ohmic, as demonstrated above and the light bulb is non-ohmic.

5. In the column headed ‘power’ in your results table, calculate the power for the light globe. Plot a graph of power against current for the light globe

   • What relationship is suggested by this graph. As current increases at a constant rate, power increases at an increasing rate.
   • Use the formula for power (P=VI) and Ohm’s Law (V=IR) to derive an equation for power as a function of current as suggested by your graph $y=10.496\times x^2+0.0717\times x-0.0136$.

6. What sources of error are there in this experiment? Think about the assumptions that have been made - are they valid assumptions? (For example, it is assumed that the ammeter and wires have no resistance.)