Need new resistances

Discussion in 'Supporting Physics' started by JHRoss, May 17, 2019.

  1. Hi there,

    I have been requested 10kΩ resistances to a practical but I don't have them and I was wondering if there are some standard values of resistances which every prep room needs to have, in order to put them in my next order form.

    Regards
     
  2. It depends on your scheme of work as all the resistance practicals I've ever seen (including within the same scheme) have a seemingly random set of requirements

    We bought a whole load of substitution boxes to ease it up last year - they do any resistance you like between 1-999'999 ohms :)
     
  3. My physics tech is working through 3 gratnell trays full of resistors of every size from the looks of it.
     
  4. I have ceramic resistors in 4.7, 10 and 22 Ohm. They are good for students as they get hot but don't melt.

    I haven't needed anything with more resistance. Is it for the diode RP?
     
  5. yes 500Ω and 1 kΩ in Edexcel SP10d.1 Investigating resistors, they obviously picked 500Ω as it's half 1000Ω but the resistors are 470Ω as it's a log series.

    :rolleyes:

    got draws of 1R0 2R0 etc
     
  6. It depends on what the practical(s) is that you are doing and also how hands on you are when it comes to the upgrading/repairing of equipment. I have always worked in prep rooms filled with a good range of resistors for pretty much any job. Most suppliers sell a 'mixed' bag of resistors so at least you can have a good range to start with. Resistors are one of those items that you can spend years collecting and end up with hundreds that are never used but may always be useful.

    These ones are used for a IV curve practical where they also have to work out the value of two unknowns:
    https://uk.rs-online.com/web/p/through-hole-fixed-resistors/1639064/

    These ones were used for one of the resistance PAGs:
    https://uk.rs-online.com/web/p/through-hole-fixed-resistors/7078782/
     
  7. Nick Mitchener

    Nick Mitchener COMMITTEE

    We very rarely need resistors of that value. A few for KS5 capacitor charge decay, lower school generally use resistors up to 100 ohms all in high wattage values so they don't burn them.
     
  8. I have several Gratnell trays with values from under one ohm to even 100,000,000Ω.
    Resistors are mounted in ABS boxes with 4mm sockets. There are 'mystery resistors' which have either had the values scraped off or painted over.
    The low value resistors are all power type, ceramic or metal clad. For critical use we have +/- 0.1%, 1% as well as 5% and 10% as requested by some teachers. Very low values are riveted onto metal rather than ABS boxes which also act as heatsinks. A few examples attached below.
    Usual click on the thumbnails for a larger picture.
     

    Attached Files:

  9. Difficult to find a quantity about a class set actually
     
  10. PhysicsSimon

    PhysicsSimon COMMITTEE

    If memory serves, charging & discharging a 4700microF capacitor to/from 6V using approx 22kohm resistor takes approx 1 minute - a nice time allowing for repeats etc. Though we use resistance boxes for this so they try it with 3 different resistances. Otherwise we mainly use 22 or 10 ceramic ones so the current is within easy range of our Satz ammeters