We went through the homework, and did some more calculations of voltage, current, resistance and power.
Start doing some revision, and think about which topics you want to revise before the mock.
The mock will NOT COVER:
Chapter 11: Lenses and the Eye
Chapter 18: Motors, Generators, Transformers
We did some recap questions on specific heat capacity (see P128-9 of the textbook).
We measured the efficiency of a 12V incandescent bulb, and evaluated the result (it turned out to be an overestimate as we did not take into account heat lost to the beaker and surroundings).
Answer Q5+6 on P192 and hand in tomorrow morning before registration.
We did quite a few calculations about cost of electricity, and talked about standby power.
We made notes on the key features of the national grid. See also this video.
Answer Q2-3 on P191 and Q4 on P192. Hand in on Monday.
Read P182-3 and make notes on how to choose the correct fuse. Answer Q1 and Q2 on P183.
Read and make brief notes on calculating the cost of electricity on P187. I will post a video about this to watch for homework. Answer Q2 and Q3 on P187. It is essential that you enter the power in kW, and the time in hours into the formula, not in W and seconds as you would with most formulae.
Read and make notes on the "New bulbs for old" part of P188-9. See if you can fill out the "Lighting Choices" worksheet.
Watch this video about calculating the cost of electricity and add to your notes from the lesson if necessary.
Please correct your oscilloscope sheet using the answers provided below. Here are some more questions that you can practise with if you need them.
Watch and make notes on this video about earthing. Read P180-181 and add to your notes - particularly about the fuse protecting the live wire. We will go over this lesson and also look at RCCBs (which are mentioned on P181).
Look around your house and record the power rating of five different appliances (you will often find the power rating on a sticker on the back) - e.g. hoover, kettle, microwave, tv, radio, hairdryer, phone charger, ... Bring the list to next lesson so we can use it.
Using an oscilloscope
We practised using an oscilloscope to measure the amplitude, period and frequency of an AC voltage.
If you were not here in the lesson, then please mark your answers to the "Reading Off Oscilloscopes" sheet. If you do not get something close to my answer, try to correct. Watch the video again if necessary.
My answers were:
amplitude 0.3V, period=0.22s, frequency=4.5Hz
amplitude=0.027V, period 46ms or 0.046s, frequency 21Hz (remember you need to convert period to seconds when you use it in f=1/T)
amplitude=0.86V, period=5.6s, frequency=0.18Hz
For all of you: Watch this video about mains cables and plugs, and read P178-9 of the textbook.
Make notes on both of these and bring your notes to next lesson.
I am not here today. Here's your work.
1. Use the markscheme provided to mark and then if necessary correct your homework from last lesson.
2. Read and make notes on P178-9, and answer Q1-4 on P179. When you get home you can watch this video which will help.
3. You have watched a video about oscilloscopes but this might be a bit hard - do your best. Read the oscilloscope instruction sheet then have a go at the questions on the Reading Off Oscilloscopes sheet. If you don't have a clue what you're doing then wait till next lesson.
Watch this video which should help with the stuff you did in the cover lesson today. Add to your notes if necessary.
AC, DC and Oscilloscopes
We did some basic questions about circuits.
I introduced Alternating Current (AC) and Direct Current (DC) - see the first few minutes of this video and P176-7 of the textbook.
We used circuit building software to model an AC circuit, and then used an oscilloscope to see the voltage in a real AC circuit.
We started the questions on P177.
Watch this video about AC and oscilloscpes - you will be using them next lesson.
Answer Q1-4 on P177 and bring to next lesson.
We defined voltage and current (which you have done before in Y9).
We did some recap questions on P185 (we will go through Q3 next lesson). These involved the formulae:
Q = I x t
E = V x Q
V = I x R
Recap on rules about voltage and current in series and parallel circuits by wathcing these videos. Make notes where necessary - you have covered all of this in Y9 but you may have forgotten some of it. Be ready for a quiz next lesson.