The forces between the primary and secondary coils

Principle

This experiment demonstrates the force on a closed conductor in which current is being induced. Using DC in the primary coil, there is a pulse as the power is turned on and the coil is forced away. Using AC, the coil hovers over the primary coil.

  Model of a high voltage long distance line

Principle

When electrical energy is transmitted over long distances, it is unavoidable that there will be losses due to resistance in the lines. Using transformer stations and high-voltage transmission lines can drastically reduce such losses. To model such lines, two wires of 1 m in length and total resistance of 100 ohms are connected to a 6-V/0.5-A light bulb and an AC voltage of 6 V is transmitted along them. Under these circumstances the lamp does not light. However, if two step transformers are set-up as transformer stations to increase the voltage in the simulated transmission lines to 1000 V and then convert it back down to 6 V immediately before the lamp, the lamp will light up with its normal brightness.

  Galvanometer

Principle

This galvanometer kit can be used to demonstrate to students the principle design features and functioning of a galvanometer.

 

  Current-carrying conductors in magnetic fields

Principle

If a current-carrying conductor is inside a magnetic field produced by a magnet, then there will be an interaction between the two magnetic fields, whereby both the magnet and the conductor will exert forces on one another.

  Dependence of the Lorentz force on the current intensity, conductor length and field direction

Principle

The Lorentz force acting on a straight conductor in a magnetic field is proportional to the current and to the length of the conductor. The direction of the force is determined by the direction of the current and the direction of the magnetic field (right-hand rule, cross product).

  Field distribution and field strength in the area around a straight conductor

Principle

The magnetic flux density in the field of a straight conductor is inversely proportional to the distance from the conductor. In the experimental set-up pictured here, a high-current transformer generates an alternating current of approximately 100 A, which flows through a rectangular electrical conductor. In combination with the high sensitivity of the teslameter, this high current makes it possible to measure magnetic field strength very precisely at distances up to more than 10 cm. The series of measurements begins at a distance r of about 1 cm and increases incrementally to 10 cm at constant current, whereby the probe is moved along an extended radius of the conductor at a constant height.

  The law of induction for sinusoidal alternating fields

Principle

The voltage induced is proportional to the number of windings and to the surface area of the induction coil. For sinusoidal alternating fields, it is also proportional to the current and to the frequency of the current generating the field.

  Waltenhofen Pendulum

Principle

When a massive body made of conductive material moves through a magnetic field, eddy currents are induced. According to Lenz’s law, the body is then subjected to a force which is opposed to the cause of the eddy currents, i.e. the motion of the pendulum. The braking action increases with the strength of the magnetic field. If slits are cut into the body, this reduces the generation of the eddy currents.

  Rotary motion by turbulent flow - principle of the alternating current meter

A metal disc rotates on a bearing-mounted shaft in the presence to two out-of-phase alternating magnetic fields. Eddy currents are induced in the disc and forces are imparted onto this current-carrying conductor. Out-of-phase alternating fields also cause the rotational movement in an AC electricity meter.

  Magnetic moment in the magnetic field

A conductor loop carrying a current in a uniform magnetic field experiences a torque. This is determined as a function of the radius, of the number of turns and the current in the conductor loop and of the strength of the external field.

Tasks

Determination of the torque due to a magnetic moment in a uniform magnetic field, as a function of the strength of the magneticfield, of the angle between the magnetic field in the magnetic moment of the strength of the magnetic moment.

  Magnetic induction

A magnetic field of variable frequency and varying strength is produced in a long coil. The voltages induced across thin coils which are pushed into the long coil are determined as a function of frequency, number of turns, diameter and field strength.

  Magnetic induction

A magnetic field of variable frequency and varying strength is produced in a long coil. The voltages induced across thin coils which are pushed into the long coil are determined as a function of frequency, number of turns, diameter and field strength.

  Inductance of solenoids

A square wave voltage of low frequency is applied to oscillatory circuits comprising coils and capacitors to produce free, damped oscillations. The values of inductance are calculated from the natural frequencies measured, the capacitance being known.