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Switeches, Fuses,etc
Bio Med Tech course 1
Question | Answer |
---|---|
What is a switch? | It is a device that is used to OPEN or CLOSE a current path |
What happens when a switch is open? | The switch does not allow current to flow. The switch provides MAXIMUM resistance. |
What happens when a switch is closed? | The switch allows current to flow. The switch provides MINIMUM resistance |
What are four types of switches? | Toggle. Slide. Rotary. Push Button |
What reference designation is used for Switch? | "S" is represents switch |
Switches are shown on schematics in what positions? | Normally Open (NO) or Normally Closed (NC) |
What happens to a (NC) switch while being depressed? | The (NC) switch is opened. |
What happens to a (No) switch while being depressed? | The (NO)switch is closed. |
How is a switch identified? | A switch is identified by the number of poles and throws. |
What kind of switch opens or closes one current path? | It's a Single Pole (SP) switch |
What kind of switch opens or closes two current paths? | It's a Double Pole (DP) switch |
How does the (DP) switch show that it connected with each other? | It will have a dotted line which indicates that the arms are mechanically connected. The mechanical connection indicates that one switch is used to move both arms. |
How many paths can a (ST)switch route? | The (ST)switch can route current in only one path. |
How many paths can a (DT)switch route? | The (DT)switch can route current in either of two paths. |
What switch has two poles and opens or closes one current path for each pole? | A Double Pole Single Throw (DPST). A dotted line indicates that the arms are mechanically connected. The mechanical connection indicateds that one switch is used to move both arms. |
What is the purpose of a switch? | The purpose is to make or break one or more current paths |
What is a toggle switch used for? | It's mainly used in most homes to turn something on or off. Ex. Ligts Toggle switches are identified by the toggle or bat that is used to open or close the switch. |
What kind of toggle switches are there? | Single Pole Double Throw (SPDT) Double Pole Double Throw (DPDT) 4 Pole Double Throw (4PDT) |
How are rotary switches identified? | They are identified by a shaft that is rotated or turned. The rotary switch can complete many current paths. Used on old tvs to change the channel |
Rotary switches have what? | They have wafers or decks. Each wafer contains the contacts that complete the current path |
What are push button switches used for? | They are used for power application and as a selector. They can be open or closed. Some tvs use the push button switch to apply power or select channels. |
Which switch is similar to the toggle switch? | The slide switch is similar with one exception the arm is slid back and forth. Some tv adapters use slide switches to select between tv and game |
What is a protection device used for? | The protection device senses an excessive increase in current flow and opens the ciruits before damage occurs. |
What are the two types of protection devices? | They are Fuses, and Circuit Breakers |
What is a fuse made of? | The fuse body is made of glass or ceramic material with a wire connected to metal end caps. The glass body allows for a visual check to determine if the fuse is good or bad |
When a fuse is placed in a circuit what happens? | The current is able to flow through the wire. |
What happens if the current exceeds the limit set by the fuse? | The wire in the fuse heats up and melts. This opens up the current path. |
Fuses are rated by what? | AMPS |
What type of fuses are there? | Fuses are classified as: Fast Action, or Slow-Blow |
What does a fast action fuse do? | The fast action fuses "melt" in less than one second after an overload condition |
What does a Slow-Blow fuse do? | Slow-Blow fuses "melt" approximately one to thirty seconds after an overload condition, depending on the amount of overload. |
When are Slow-Blow fuses used? | They are used when a momentary overload condition will not damage the circuit |
The circuit breaker is used to? | It is used to break the current path. |
If an overload condition happens to a breaker what happens? | The breaker remains operational unlike the fuse. |
Whats good about a circuit breaker? | Circuit breakers do not "melt"; they open and can be reset |
How does a circuit breaker operate? | It automatically opens when an overload condition exists. Once the overload condition is corrected, the circuit breaker can by manually closed |
How are circuit breakers classified? | As Magnetic or Thermal |
How does a magnetic circuit breaker work? | It produces a magnetic field as current flows through the device. When current flow exceeds the limit set by the device, the magnetic field opens the circuit breaker. |
How does a thermal circuit breaker work? | It operates on the principle of temperature. Current flow produces heat, when there is too much current flow it overheats the bimetallic element. When the element overheats the circuit breaker opens. |
What is the resistance of an open switch? | Maximum |
A switch in the open position? | Stops current flow |
Which switch rotates on a shaft? | Rotary |
Magnetic circuit breakers operate when excessive current flow? | Produces a strong magnetic field |
Protection devices open when? | Current flow is excessive |
What can switches do? | Route current in one or more directions |
What is (DIPP) | Dual inline pin package |