# g482 physics circuits help

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#1
http://www.ocr.org.uk/Images/58047-q...nd-photons.pdf

i dont get q4) d)

whats this arrow sign and how does it make things more variable?
0
5 years ago
#2
(Original post by nmjasdk)
http://www.ocr.org.uk/Images/58047-q...nd-photons.pdf

i dont get q4) d)

whats this arrow sign and how does it make things more variable?
The arrow against a resistor denotes the component as a variable resistor or potentiometer.

Notice there are 3 terminals to this component:

The central terminal is known as the wiper and has the same function as picking off a voltage between two series connected resistors forming a potential divider.

The variable resistance is made from a track of resistive material spread along a bar or curve shape with the ends terminated in solder tags. The wiper is able to slide up and down the track and thus it's position creates the potential divider action.

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#3
(Original post by uberteknik)
The arrow against a resistor denotes the component as a variable resistor or potentiometer.

Notice there are 3 terminals to this component:

The central terminal is known as the wiper and has the same function as picking off a voltage between two series connected resistors forming a potential divider.

The variable resistance is made from a track of resistive material spread along a bar or curve shape with the ends terminated in solder tags. The wiper is able to slide up and down the track and thus it's position creates the potential divider action.

im still stuck if the arrow from point A denotes the resistore as variable (and i sure thats not how variable resistors are displayed), even than where is the point A of that circuit connected to.

if you read the previous part of the questions it says between point A and B their is a an ammter voltmeter etc etc so im sure its not reffering to the variable resistance.

thanks for the help btw.
0
5 years ago
#4
(Original post by nmjasdk)
im still stuck if the arrow from point A denotes the resistore as variable (and i sure thats not how variable resistors are displayed), even than where is the point A of that circuit connected to.

if you read the previous part of the questions it says between point A and B their is a an ammter voltmeter etc etc so im sure its not reffering to the variable resistance.

thanks for the help btw.
I can assure you my interpretation is correct.

Both of the symbols conform to the DIN / IEC 60617, IEEE315 & BS 3939 international standards for electrical and electronic components.

Is the same as:

Your confusion stems from the wiring of the two terminal type, which is constructed by electrically connecting the wiper of the three terminal potentiometer to one of it's end terminals and thus creating a variable resistor, but..... the internal wiring is not shown explicitly.

Physically, the only difference between the potentiometer and variable resistor is that electrical connection. Thus a three terminal potentiometer can fabricate a two terminal variable resistor by externally connecting the wiper to one of the end terminals.

Take a look at the symbols in this link (compare the common European and U.S. variants), specifically the 2nd, 3rd, 5th and 6th symbols which should be self explanatory.

It does not help that the words and symbols for potentiometer and variable resistor are used interchangeably which causes confusion with inexperienced students. That's not your fault but it is a historical quirk caused by different international standards.
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