kingston mod 3 Flashcards
EZ W
sketch a graph of current against time to show what happens when an inductor circuit is isolated with a switch. Inc the axis as well as key values identified.
(im not paying to add pictures)
its an exponential reduction in current to 0.
annotate:
-time along x axis, current along y.
-max current value. (V/R)
-time constant (L/R in seconds).
-D or Discharged when current is zero.
what is a positive temperature coefficient of resistance?
a positive t.c.r means that temperature and resistance are directly proportional. When temperature increases, so does the resistance. When temperature decreases, the resistance will decrease too.
What affects will a second parallel-connected inductor have on the time constant?
In parallel, 1/Lt= 1/L1 + 1/L2 + 1/L3…
Added inductors in parallel means less inductance and results in a steeper discharge curve.
The time constant will reduce.
Factors affecting resistance with explanations.
p (ro) - the coefficient of resistance for a material. This is a material inherent resistance to electron flow, a higher p value will result in higher resistance and less electron flow.
Temperature - materials will either become more or less resistant depending on if their temperature coefficient of resistance is positive or negative.
Length and Cross sectional area- Materials with more length and a higher cross sectional area have more material for electrons to have to pass through. Resistance is directly proportional to CSA and L.
how do you work out terminal voltage and capacity of 3 batteries in parallel?
Vt= (V1+V2 +V3) /3 Voltage will be the same value as a single cell.
It= I1 + I2 + I3 capacity increases
how do you work out the terminal voltage and capacity of batteries in series?
Vt=V1 + V2 + V3 Voltage increases
It= (I1 + I2 + I3) /3 Capacity is the same value as a single cell.
How to calculate total resistance of a circuit.
V=I*R
For resistors and in parallel, use ‘1 over rule’. In series, use the sum of the resistors.
Work out the parallel section first the add it to the series resistance.
How to calculate the total current in a circuit.
I= V/R
Current is equal to the EMF or voltage divided by the total resistance of the circuit.
Work out resistance first. In parallel, use ‘1 over rule’. In series, use the sum of the resistors.
How to calculate the voltage at a point in a circuit.
TBH i dont know, my bad gang.
How to calculate the power dissipated in a resistor.
P= VI or P= I^2R
what is conventional flow and how does it differ from electron flow?
Conv flow= positive to negative current flow.
Electron flow= negative to positive current flow.
What is hard iron and soft iron, what are they used for?
Hard iron is difficult to induce magnetism in but stays magnetised well. It is used for permanent magnets.
Soft iron is easy to magnetise but loses its magnetism easily. It is used for temporary magnets.
that resistance band colour question. (just remember the value, it probably wont change in the exam.)
13000 with a 5% tolerance (+ or minus 6500)
123500-136500 Ohms each.
in parallel: 61750-68250 Ohms.
work done in a point of a circuit.
Work done ( J ) = power x time
power = voltage x current
Impedance of an amp.
-necessary load has to match the impedance of the amp. If the impedance is 45 Ohms, the output must be 45watts.
-the necessary load will dissipate half the power.
