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electromagnetism
and electromechanics
| Question | Answer |
|---|---|
| What phenomenon did Luigi Galvani observe in the late 1700s? | Frog legs twitched when touched by two different metals, similar to an electrostatic charge. |
| What did Alessandro Volta create using zinc and copper plates? | A Voltaic pile, which is a precursor to the modern battery. |
| What is electric potential measured in? | Joules per coulomb, or volts. |
| What did Hans Oersted demonstrate in 1820? | A direct link between electric and magnetic phenomena. |
| What happens to a magnetic compass when electric current passes through a wire? | The compass needle swings to point straight at the wire. |
| What induces a magnetic field according to electromagnetism? | Any change in motion, as well as electrons flowing through a wire. |
| What is a solenoid? | A coil of wire. |
| How can the intensity of a magnetic field in a solenoid be increased? | By stacking more loops on top of each other. |
| What is an electromagnet? | A current-carrying coil of wire wrapped around an iron core, which intensifies the induced magnetic field. |
| What did Michael Faraday conclude about electric current and magnetic fields? | An electric current cannot be induced in a circuit merely by the presence of a magnetic field. |
| What is electromagnetic induction? | An electric current is induced in a circuit if some part of that circuit is in a changing magnetic field. |
| What factors affect the magnitude of induced current according to Faraday's Law? | The strength of the magnetic field, the velocity of the magnetic field, the angle of the conductor, and the number of turns in the conductor. |
| What is mutual induction? | The induction of electricity in a secondary coil by a moving magnetic field. |
| What is self-induction? | An induced current flows in a direction that opposes the action that induced it, as described by Lenz's law. |
| What is the principle behind electric motors? | An electric current produces mechanical motion. |
| What is the principle behind electric generators? | Mechanical motion induces electricity in a coil of wire. |
| What is an electric generator? | A device where a coil of wire is placed in a strong magnetic field between two magnetic poles. |
| What happens to the magnetic field when the current in an electromagnet is varied? | The magnetic field also changes, inducing a current in a nearby coil. |
| What is the effect of a charge at rest on a magnetic field? | It produces no magnetic field. |
| What forms can electromagnetic induction take? | Mutual induction and self-induction. |
| What happens to magnetic field lines in a loop of wire? | They form concentric circles and overlap inside the loop, creating a strong magnetic field at the center. |
| What is the role of an iron core in an electromagnet? | It intensifies the magnetic field by concentrating the magnetic field lines inside the core. |
| What is the significance of Oersted's experiment? | It demonstrated that electricity can generate magnetic fields. |
| What is Lenz's law? | An induced current flows in a direction that opposes the change causing it. |
| What is the principle operation of an electric generator? | An electric generator converts mechanical energy into electrical energy by rotating a coil of wire in a magnetic field. |
| What energy sources can supply mechanical energy to an electric generator? | Water, steam, or turbine blades in a nuclear power plant. |
| What is the efficiency of an electric generator? | The conversion process is not 100% efficient due to frictional losses and heat losses in electrical components. |
| What is the main function of an electric motor? | An electric motor converts electrical energy into mechanical energy. |
| What must occur for the motor effect to take place? | A conductor must carry a current and be located in a magnetic field. |
| What does the Right Hand Rule indicate? | The thumb indicates the direction of conductor movement, the index finger indicates the direction of the magnetic field, and the middle finger indicates the direction of electron current. |
| What type of motor is used with x-ray tubes? | An induction motor. |
| How is the current produced in the rotor of an induction motor? | The current is produced by induction, as no electric current is passed directly to the rotor. |
| What are the three parameters controlled on the x-ray console? | X-ray tube voltage (kV), tube current (mA), and exposure time (seconds). |
| What is the primary function of a transformer? | To change the size of the input voltage, producing high or low voltages. |
| What is a step-up transformer? | A transformer with a turns ratio greater than 1, increasing voltage from the primary to the secondary side. |
| What is a step-down transformer? | A transformer with a turns ratio less than 1, decreasing voltage from the primary to the secondary side. |
| What is the transformer formula for voltage? | Vs/Vp = Ns/Np, where Vs is secondary voltage, Vp is primary voltage, Ns is number of turns in the secondary, and Np is number of turns in the primary. |
| What is a closed-core transformer? | A transformer built around a square core of ferromagnetic material, designed to reduce energy losses. |
| What is an autotransformer? | A transformer with only one winding that acts as both primary and secondary, suitable for small voltage adjustments. |
| What is a shell-type transformer? | A transformer that confines more magnetic field lines, making it more efficient than a closed-core transformer. |
| What is the main advantage of a shell-type transformer? | It is more efficient than other transformer types due to better confinement of magnetic field lines. |
| What is the role of the external magnetic field in an induction motor? | It is supplied by fixed electromagnets called stators, which energize in sequence to produce a changing magnetic field. |
| What happens to the rotor in an induction motor when the external magnetic field changes? | The rotor attempts to align its magnetic field with the external electromagnets, causing it to rotate. |
| What is the significance of the turns ratio in transformers? | It determines whether the transformer is a step-up or step-down transformer based on the voltage change. |
| What is the relationship between voltage and turns ratio in transformers? | The voltage change across the transformer is proportional to the turns ratio. |
| What is the main job of a transformer in an x-ray machine? | To produce high and low voltages for the x-ray system. |
| What type of current do generators for x-ray systems use? | Higher voltages (440 V) compared to standard household voltage (120 V) and typically use AC. |
| What is the effect of frictional losses in electric generators? | They contribute to the inefficiency of the energy conversion process. |
| What is the mechanical motion produced by an electric motor? | A rotation of the current loop in the magnetic field. |
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