Data Collection and Processing:
I → Current flowing through solenoid
B → Magnetic field strength
Raw Data Table showing magnetic field within a solenoid for a particular value of current flowing through it.
Graph of current passing through the solenoid vs magnetic field strength inside the solenoid
Slope of best fit line = -0.406 mT A-1
Maximum slope = -0.289 mT A-1
Minimum slope = -0.497 mT A-1
Thus, slope = -0.406 ±0.117 mT A-1
As we already know,
Where B → Magnetic field strength
→ permeability of free space
n → number of turns per unit length of solenoid
I → current passing through solenoid
Number of turns in solenoid = 250
Length of solenoid = 10 cm = 0.1 m
Thus, n = 2500
From equation, = = slope of graph plotted = -0.406 ±0.117
= -0.406 ±28.8 % mT A-1
Thus, -1.62 X 10-4 ±28.8% mT A-1
= (-1.62 ±0.47) X 10-4 mT A-1
Thus, = (-1.62 ±0.47) X 10-7 T A-1
The literature value for permeability of free space = 4π X 10-4 T A-1
= 1.26 X 10-3 T A-1
Weaknesses in the experiment:
- There were a number of electrical devices close to the solenoid. Each of theses devices, namely the laptop, LabPro, Power Pack and variable resistor had current carrying conductors. These created a magnetic field which interfered with the magnetic field of the solenoid.
- The magnetic field was not constant within the solenoid.
- If the sensor is kept in one position, the background field of the earth will not affect the magnetic field strength.
- The sensor measures the component of the magnetic field that is perpendicular to the white dot on the end of the sensor tip.
Obtained from Physics IBO Data Booklet