Wordwall Revision Games

Practice your Physics using these Wordwalls, don’t forget this forms only PART of your revision.

Sorry I don’t know why some of these wont embed, I’ve had to post them as links. I hope you can still get to play.

Continue reading “Wordwall Revision Games”

Week 1: Intro to N5

Focus

  • Know what to expect on the National 5 Physics course
  • Understand the Course Structure
  • Know where to access materials
  • Find good places to go for online help.
  • Know about Units, Prefixes and Scientific Notation

Success Criteria

  • Understand the make up of the SQA N5 Physics Course
  • Get 90% or more on the weekly Friday Review assessment
  • Complete the tasks on Units, Prefixes and Scientific Notation to a high standard

TASKS

  • Check out the National 5 compendium and save your own copy in an editable form.
  • Read through the whole of Mrsphysics.co.uk/n5 front page
  • Go through the compendium and mark off the content that you feel you have already covered in BGE. You could do this electronically if you want (NB Capital P in wingdings 2 gives a nice tick and capital O gives a cross).
  • Check through the course content from the SQA website
  • Watch Mr Mitchell’s Introduction to N5 Physics
  • Watch Mr Mitchell’s Greek Letter Video
  • Watch Mr Mitchell’s Video on Units, Prefixes and Scientific Notation
  • Read the material in the Intro of the Compendium.
  • Make notes on the Compendium content 0.2,0.3,0.4. and pages 21 to the end.
  • Work through material on rearranging equations
  • Answer the questions from the Learning Outcome Question Booklet on Units Prefixes and Scientific Notation 0.2, 0.3,0.4 or if you need the link as a pdf
  • Start making a list of Quantity, Symbol, Unit, Unit Symbol, Scalar or Vector in the Notes. NB Colum 3 needs to be much wider than most and column 1 needs to fit in gravitational field strength, but columns 2, 4 and 5 only need to be a few letters wide. Keep this up to date, and we’ll have a quiz as to who can get the longest list from all the quantities you’ve met in the BGE.
  • Do the Quiz on TEAMS- you’ll need to score 9/10 or more so do some revision.
  • Let me know if you don’t have a CASIO 83 or 85 calculator.
  • ….and finally, ask any questions that you have or anything that you need to be explained in more detail.

WELCOME TO THE TEAM.!

Signature
April 2020

A.C/D.C

As Mr Clydesdale says “A very good band”

The date is really 2020, but I need this post under the main Electricity notes section.

Mr Sharkey demanded I take screenshots of the traces for his OneNote ClassNotebook as he was made to leave against his will! So he asked, and I did!

Here are the A.C /D.C traces

from Nat 5C 2020

We’ve plugged in a 1.5 V cell to the picoscope, put a voltmeter in parallel and noted the reading on the voltmeter and the looked at the value on the picoscope.

The picoscope was picking up some of the electrical signals from the computers and power around the room.

Notice on these images the reading on the picoscope and the voltmeter are the same. The cell is a source of D.C, direct current. In direct current the current /charges only flows in one direction. The free electrons in the ciruit are always drifting around the circuit in one direction.

When the polarity is reversed (swapping the positive and negative connections to the cell) the trace moves below the zero line showing that the current is now in the opposite direction. The voltmeter reads -1.5 V (the negative indicating that the current is in the opposite direction).

When we connect up to the A.C supply of the usual school power supplies we can see that the trace indicates the current flows in both directions. We can tell this as the trace of the voltage goes above and below the 0 V line on the picoscope. The trace shows a wave indicating the voltage and hence current is changing direction and magnitude many times per second. In the case of the mains voltage the frequency of the supply is 50 Hz.

Notice that the reading on the voltmeter reads 6.69 V. The power supply is set to 6V, but the peak of the trace is greater than this, about 9.5 V. The peak voltage of an A.C. trace is always greater than the quoted voltage of the supply. This is because we want to be able to compare A.C and D.C traces and so the quoted value is 1.414 times smaller than the peak voltage, try this.

When the polarity is reversed it makes no difference to the trace.

Another power supply in the Department is the 5.0 V regulated power supply. We can see this is a D.C trace and that the value of the voltage and hence the current is steady.

We can see when the polarity is changed (the connections to the power supply are swapped over) We can see the the trace of the voltage goes below the zero line, indicating the current is moving in the opposite direction. The voltmeter reading is the same as the value on the picoscope.

However, when we connect the picoscope to the usual Lockmaster power supply on the D.C. setting we get a rather unusual trace. The trace is D.C, remember direct current tells us that the current remains in one direction. However, the voltage and hence current isn’t constant. This is an unsmoothed D.C trace, and is common in cheaper power supplies. The trace never goes below the zero value on the screen.

Reversing the polarity shows us that the voltage is opposite, we get a negative value on the power supply but the trace never goes above the line. The current remains in one direction.

So in summary

In DIRECT CURRENT the current always moves in one direction.

In ALTERNATING CURRENT the current changes direction, usually many times per second. The current also usually changes magnitude (size).

With cells or regulated power supplies the D.C trace gives a constant value. In an unregulated trace the current also changes magnitude, but never direction.

Signature
December 2020
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