# Relationship between current and magnetic field of a loop lab To measure and determine the relationship between a magnetic Theory states that the magnetic field produced by a circular loop of current-. A wire carrying electric current will produce a magnetic field with closed field lines of the current, and the fingers curl in the direction of the magnetic field loops .. Magnetic Field: A schematic illustrating the relationship between motion of. We noted earlier that a current loop created a magnetic field similar to that of a bar . in a general relationship between current and field known as Ampere's law .

## Magnetic Fields Lab

Throughout the experiment, we used several different cards bearing foil current loops of different lengths, L. Figure 1 gives one example. Experimental Setup Using a balance, we first measured the mass of the magnet. We then supplied a current through the wire loop inserted between the poles of the magnet and measured the apparent mass of the magnet.

While keeping the length of the wire loop constant, we varied the amount of current supplied to the circuit. We then held the current constant and varied the length of the wire loop exposed to the magnetic field by changing the card inserted in the circuit. We preformed six trials each for both the constant length and constant current parts of the experiment. We measured all lengths with a ruler and all currents with an ammeter.

We analyzed our data using LinReg. Data and Data Analysis: The magnetic force on a current-carrying wire can be measured using a current balance. This force on the magnet causes the normal force of the balance on the magnet to change, as shown by the free body diagrams below Figure 2. Free body diagrams for the magnet a when no current is applied and b when current is applied. The magnitude of the normal force changes when a current is present due to the presence of the magnetic force between the wire and the magnet note: Figure 2 shows the normal force increasing due to a downward force of the wire on the magnet; however, the normal force will decrease if the magnetic force is exerted in the opposite direction.

The magnitude of the magnetic force, and the magnitude of the change in the normal force, is the same in both situations. Therefore, the normal force gives a measure of the apparent weight of the magnet where Fnormal is the normal force, ma is the apparent mass of the magnet, and g is the acceleration due to gravity 9. From Figure 2bit is clear that the magnetic force is equal to the difference between the normal force and the weight of the magnet, or the difference between the actual and apparent weights of the magnet.

The mass of the magnet is Table 1 shows our data and calculations of magnetic force, calculated using the equation above, for both the constant length and constant current portions of the experiment. See Figures 3 and 4 for graphs of our data for the constant length and constant current trials, respectively.

Relationship between the current in a wire exposed to the magnetic field and the magnetic force on the wire. Relationship between the length of wire exposed to the magnetic field and the magnetic force on the wire.

• Physics 120 Fall 2013/Appendices/Sample Lab Report

Our data confirm the linear relationship between I and F. For your data from Part 2, plot a graph in Graphical Analysis of B vs. The graph of the slope is 6. The value is 6. The percent difference is 2.

Magnetic Field Due to Current Carrying Circular Coil

Conclusion During part one of the experiment, magnetic field strength was measured as a function of radial distance from a conductor. First, a piece of polar graph paper with concentric circles starting at a diameter of 0. The paper was placed on the plastic table of the apparatus and was aligned using a compass so that the parallel lines on the sheet were pointing north. The paper was then secured to the apparatus using tape. The high amperage DC power supply was connected in series with a high power resistor and the aluminum wire at the side and on top of the apparatus.

The magnetic field sensor was zeroed and the DC power supply was set to 7 A. With the current on and kept constant, the magnetic field strength was recorded at each circle on the polar graph paper by holding the sensor in line with the parallel lines on the sheet and so that the white dot on the sensor was on the left and at a 90o angle with the parallel lines pointing north.

The magnetic field strength was recorded using Vernier Lab Pro. This value was recorded along with the respective radius. Graphical Analysis was used to plot B vs. The resulting slope was 9. It was somewhat difficult to get accurate readings at the smaller radii, which negatively affected this correlation. The data followed the expected trend of decreasing in magnetic field strength as the radius increased.

Possible sources of error include the difficulty of aligning the sensor perfectly along the radius of each circle, and it was also a challenge to get an accurate reading from the sensor as the readings kept jumping around.

### Magnetic Fields Lab

During part two of the experiment, magnetic field strength was measured as a function of the number of turns in a wire. First, the power supply was turned off and the center aluminum wire was removed along with the top table of the tangential galvanometer. The magnetic field sensor was inserted into the side of the cylindrical support by screwing it into the side of the top table support using a threaded plastic bushing.

The white dot of the sensor was aligned to be in the center of the cylindrical support with the white dot facing upward.