(1) increasing the wire’s length
(2) increasing the wire’s resistivity
(3) decreasing the wire’s temperature
(4) decreasing the wire’s diameter
Explanation :
We know that the resistance of the wire is given by :
Where
is the resistivity
l is the length of the wire
A is the area of the wire.
Another factor on which the resistance of wire depends is temperature. It is given by :
So, it is clear that the resistance of the wire is directly proportional to the temperature. It we want to decrease the resistance of the piece, its temperature should be decreased.
So, the correct option is (3) " decreasing the wire’s temperature ".
Decreasing the wire’s temperature decreases the resistance of a piece of copper wire.
Resistance is a type of opposition force due to which the flow of current is reduced in the material or wire. Resistance is the enemy of the flow of current.
The relation of resistance with length and thickness is given by ;
The value of resistance is directly propotional to length and inversly propotional to the area or thickness of the wire.
As the value of temperature increases, the value of resistance in the material is increasing. Length, temperature, and thickness are the factors that affect the resistance of a material.
Resistance of the wire is directly propotional to the temperature. On decreasing the temperature the resistance of the wire is also decreasing.
Hence decreasing the wire’s temperature decreases the resistance of a piece of copper wire.
To learn more about the resistance refer to the link;
B. ultrasonic vibrations.
C. sympathetic vibration.
D. resonance.
A
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Answer:
B. the acceleration of a skydiver depends upon the force of gravity and wind resistance
Explanation:
Newtons second law of motion states that: the force (F) acting upon an object is directly proportional to the mass (M) of the object and the acceleration (a).
Basically this law states that the acceleration of a body is dependent on the force and mass of the body. If the force exerted on the body changes the acceleration will also change. and if the mass of the body changes, the acceleration will also be affected
from the options, the only option that refers to acceleration is option B
more than 50% but less than 100%
50%
less than 50% but more than 0%
100%
Answer:
50% if light is unpolarized
100% if light is horizontally polarized
0% if light is vertically polarized
Explanation:
A polarizer has an axis that "blocks" the component of light in the direction perpendicular to the direction of the polarizer axis.
When unpolarized light passes through a polarizer, the intensity of light is reduced to , where is the initial intensity of the light: this is because only the component of the light parallel to the axis of the polarizer will pass through, and this component makes 1/2 of the incident light intensity. In this case, since the axis of the polarizer is horizontal, only the horizontal component of the light will pass through, while the vertical component will be blocked. So in this case the final intensity will be 50% of the initial one.
On the other hand, if the incoming light is already horizontally polarized (same orientation as the polarizers), there is no vertical component to block, so all the light passes through the polarizer; therefore, the final intensity will be 100% of the original intensity.
Finally, if the incoming light is vertically polarized, no light will pass through it, because the polarizer's axis is horizontal, so it will block all the vertically polarized light: so the final intensity will be 0% of the original intensity.
All of this is after passing the 1st polarizer; so, after passing the 1st polarizer, the light is now horizontally polarized. Then, the intensity of the light passing through the 2nd polarizer is given by Malus' Law:
where is the angle between the axes of the two polarizers. Since here the two polarizers axes are parallel to each other, , so , and so the intensity after the 2nd polarizer is exactly the same as the intensity after the 1st polarizer.