Topics: Magnetic field, Transformer, Electromagnetism Pages: 4 (1124 words) Published: November 12, 2013

PHY 114 Lab Report

11/05/2013

Abstract:
The purpose of this experiment was to look at Michael Faraday and Joseph Henry showed in the 1830’s that a changing magnetic field could cause and induced emf electromotive force = voltage in a circuit. Practically, this means that when a copper pick-up coil is placed inside a solenoid whose magnetic field varies with time, current will flow in this coil even if there is no voltage source physically connected to it. This kind of induced emf is seen everywhere in the modern world in the propagation of light and radio waves, in transformers and generators, or in induction coils that give the spark for the car engine. The induced emf is proportional to the number of turns Nc in the “pick-up” coil and is related to the rate of change in the magnetic flux F the pick-up coil. If the magnetic flux F is in units of Webers ,time t in sec, the induced voltage Vemf will be in Volts. For a coil of fixed size, the flux F inside the coil is given by, where B is the intensity of the magnetic field crossing the coil, in Tesla (T), and Ac is the effective cross-sectional area of the coil in square meter (m^2)

For this simple relation to be true the magnetic field has to be perpendicular to the area Ac of the pick-up coil (parallel to the axis of the coil). If the source of the changing magnetic field is a solenoid, a coil that is much longer than it is in diameter, the magnitude of the produced magnetic field inside it is Where Ns is the total number of turns of the solenoid of length ls and I represent the instantaneous.

Objective:
The objective of this lab was to verify Fraday’s law of induction by measuring the emf generated in a small coil and comparing it with the calculated value; to investigate the relationship between the emf and the frequency of the driving signal.

Procedure:
We have to connect the circuit, then set the function generator output to the triangle signal of...