Please enable JavaScript.
Coggle requires JavaScript to display documents.
What factors affect electromotive force? - Coggle Diagram
What factors affect electromotive
force?
Dependent Variable
Electromotive Force (V)
Electromotive force is equal to the difference in magnetic flux passing through the loop of the wire per unit time.
Current (A)
The current through the loop of wire changes according to Ohm's Law, I=V/R. This means that current changes depending on electromotive force, which is the derivative of magnetic flux passing through the loop of wire.
Independent Variable
Number of turns in coil
The number of turns in the coil where current is being induced changes the electromotive force directly proportional to the number of turns.
Method of changing variable
Wrap wire around object (pipe) the required number of times.
Difference in Magnetic Field Strength
The difference in magnetic field strength is directly proportional to the difference in magnetic flux passing through the loop of wire, meaning it would also directly proportionally affect the electromotive force.
Method of changing variable
Different strength permanent magnet can be used
Current through electromagnet can be changed.
Perpendicular Area
The perpendicular area of the coil is directly proportional to the magnetic flux flowing through the coil. This means the perpendicular area would affect the electromotive force directly proportionally.
Method of changing variable
Wrap wire around different objects to change perpendicular area of coil. The dimensions of the objects can be measured to calculate the perpendicular area.
Difference in time
The difference in time is inversely proportionally to the electromotive force.
Method of changing variable
If an AC is run through a solenoid to produce an alternating current, the frequency can be changed by using a frequency changer.
If an electric motor is used to make a winch and is then used to move the magnet or coil, the radius of the shaft of the winch can be changed to change the speed at which the flux is changed.
If gravity is used to change magnetic flux, the magnet or loop can be dropped from a higher or lower height, to increase or decrease the time allowed for acceleration.
If rotating coil is used to change magnetic flux, a gear system can be used to change the speed at which the coil spins.
Possible Controlled Variables and control methods
Time taken for magnetic flux to change
The time taken for magnetic flux to change can be controlled by passing AC current through a solenoid, changing the magnetic field at a rate equal to the frequency of the AC.
If wire or magnet is being moved, a motor can be used to pull the objects in a winch setup, to ensure the movement speed of the objects is constant.
Magnetic field strength
If solenoid is used to produce magnetic field, current can be measured by an ammeter in series to ensure the current does not change. The same solenoid would also be used for all trials, since the dimensions of the solenoid such as length and number of turns also affect the magnetic field strength.
If a permanent magnet is used, the same magnet should be used for all trials.
Perpendicular area
The wire is wrapped around some object with a uniform cross sectional area, such as a cylinder, and this cylinder is used for all trials.
Number of turns in coil
The number of turns can be controlled by wrapping the wire only the required number of times. The number of turns in the coil would not be changed between trials.
Wire resistance
All factors affecting the resistance of the wire can be controlled excluding temperature. To do this, the same wire is used for all trials.
Uncontrolled Variables
Temperature of wires
The temperature of the wires cannot be controlled, since the temperature will be changed by current flowing through and causing resistance. This cannot be controlled, but can be mitigated by allowing time for the wires to rest between trials.
Method of changing magnetic flux to induce electromotive force
AC current through solenoid
AC current through a solenoid would produce a magnetic field that alternates at the rate of the AC frequency
The magnetic field at the centre of the solenoid can be calculated using the formula B=µNI/L, where µ is permeability of free space, N is the number of turns in the solenoid, I is the current flowing through the solenoid and L is the length of the solenoid.
Moving loop away/towards from magnet
Moving the loop away from or towards the magnetic field would change the magnetic flux through it, thus inducing an electromotive force.
Loop can be moved by electric motor at acting as a winch at a constant speed.
Loop can be moved by using gravity
Gravity would accelerate the falling loop of wire, meaning the speed at which the loop would move is not constant.
Moving magnet through loop
Permanent or electromagnet can be moved through a loop to change the magnetic flux through the loop
Electric motor could be used to make winch to pull through at constant rate.
Gravity could be used to move magnet through loop
Gravity accelerates falling magnet, meaning rate of movement is not constant
Turning on/off electromagnet
If an electromagnet is turned on or off, the magnetic flux through the loop can be changed, therefore increasing
Turning electromagnet on/off does not have a measurable difference in time, therefore making it not viable.
Turning loop of wire
By turning a loop of wire inside a magnetic field, the area perpendicular to the field can be changed, which also changed the flux, which induces an electromotive force in the loop.
Loop of wire can be turned using electric motor