Normally, when something gets colder, its electrical resistance gets smaller. This is true of component-A in the drawing ... a simple resistor.
The component labeled 'B' has a strange and unusual symbol, and it's not a simple resistor. It's a "thermistor". The word "thermal" always has something to do with heat, and "thermistor" comes from "thermal resistor. These things can be manufactured either way ... using different materials, a thermistor can be manufactured so that its resistance goes UP, or goes DOWN, or doesn'tchange when it gets colder. I'm pretty sure that's what's going on here.
When this circuit gets colder, resistance-A gets smaller, but resistance-B either gets bigger OR doesn't change. Either way, the voltage across B increases. Since the LED is connected directly across B, the current through it depends on that voltage, so the LED gets more current, and becomes brighter, when A and B both get colder.
This circuit could actually be a very useful device. If you took out the LED and put a voltmeter in its place, then the reading on the voltmeter would tell you the temperature of wherever you put the two components A and B.
Answer:
1 m = 3.28 ft
1 m^2 = 10.76 ft^2
1560 ft^2 / 10.76 ft^2 / m^2 = 145 m^2
Angular acceleration = (change in angular speed) / (time for the change)
Change in angular speed = (speed at the end) - (speed at the beginning)
For this fan, speed at the end = 7700 rpm, speed at the end = 0 .
Change in angular speed = -7700 rpm
Angular acceleration = (-7700 rpm) / (2.5 sec)
<em>Angular acceleration = -3,080 rev per minute / sec</em>
That's a perfectly good and true answer to the question, but the units are ugly. We really need to fix the units, and convert them into something prettier before we hand in this assignment.
1 rev = 2π radians, and
1 minute = 60 seconds .
So
Angular acceleration =
(-3,080 rev/min-sec) · (2π rad/rev) · (1 min/60 sec)
AngAccel = (-3,080 · 2π · 1 / 60) · (rev·rad·min / min·sec·rev·sec)
AngAccel = ( -102 and 2/3 · π) · (rad/s²)
<em>AngAccel = -322.5 radian/s²</em>
Answer:
Explanation:
For resistance of a wire , the formula is as follows .
R = ρ L/S
where ρ is specific resistance , L is length and S is cross sectional area of wire .
for first wire resistance
R₁ = ρ 3L/3a = ρ L/a
for second wire , resistance
R₂ = ρ 3L/6a
= .5 ρ L/a
For 3 rd wire resistance
R₃ = ρ 6L/3a
= 2ρ L/a
For fourth wire , resistance
R₄ = ρ 6L/6a
= ρ L/a
So the smallest resistance is of second wire .
Its resistance is .5 ρ L/a
