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Relays, Meters, etc
Bio Med Tech course 1
Question | Answer |
---|---|
What is Magnetism? | A force that attracts or repels certain types of metal objects. |
What are the two common permanent magnets? | Horseshoe and Bar |
What type of poles does a bar magnet have? | North pole and South pole |
All magnets have what? | Lines of force called Flux Lines. Flux lines leave the north pole and enter the south pole of the magnet. |
What does flux lines form? | Flux lines form a magnetic field around the magnet. The more flux lines a magnet has, the stronger the magnetic field. The stronger the magnetic field, the more work or attraction the magnet can perform. |
What are the two rules of magnetism? | Unlike poles attract. Like poles repel |
What are the two catergories that all materials fit into? | Non-magnetic, Magnetic |
What material is not affected by flux lines or magnetic force? | Non-magnetic materials, examples are: Glass, Plastic, Wood |
What material is affected by flux lines or magnetic force? | Magnetic materials, examples are: Steel, Iron |
What is Permeability? | It is the term used to describe the willingness of a material to become magnetized. Being permeable means that the flux lines can penetrate the material. |
What is Retentivity? | It is the ability of a material to retain its magnetism after the magnetizing force has been removed. |
What is Electromagnetism? | It is a man-made form of magnetism. It's made by applying electricity to magnetic materials. |
What is Magnetomotive force? | It is a a small circular magnetic field that is generated when electric current passes through a conductor. It's strongest close to the conductor. |
Inside a magnet, how do flux lines move? | South to North |
What rule is used to determine the direction of flux lines in electromagnets? | Left Hand Rule. Place the left hand pointing the thumb in the direction of current flow. The curled fingers point in the direction of the flux lines. |
How is the strongest magnetic field developed? | Placing loops in the conductor or wrapping the conductor around a steel or magnetic core. |
How is the magnetic field strength determined? | The number of coil windings. The distance between windings. The amount of current. Composition of the core. |
What are the three uses for electromagnets in electronics? | Relays, Circuit breakers, Meters |
How does the relay use an electromagnet? | The electromagnet attracts the metal arm of a switch. If the switch is normally open, energizing the relay closes the switch. If the switch is normally closed, energizing the relay opens the switch. |
How does a meter use electromagnetism? | Electromagnetism moves the needle of the meter. When values are measure in circuits, they are indicated by the position of the needle on a meter. |
What does a meter read? | Voltage, Current, or Resistance. |
How does meter work with a resistor? | Placing the meter leads on a resistor causes the needle to point at the value of that resistor. |
What happens when you place the meter leads across the voltage source? | The voltage source causes the needle to point at the value of the voltage source. |
What happens when you place the meter leads across an open switch? | It indicates the current of the circuit |
In a conductor, the direction of the flux lines is determined by the? | Direction of the current flow |
Increasing current flow through an electromagnet? | Increases the magnetic field |
What is a magnet that retains its ability to attract metal objects indefinitely called? | Permanent magnet |
Magnetic field strength is determined by? | The number of coil windings The distance between windings The amount of current Composition of the core |