Explanation:
Magnet: It has two poles: South pole and North pole.
Magnetic field lines are stronger near the poles of the magnet.
Same poles repel each other. There is a magnetic force of repulsion between the same poles. North- North poles repel each other.
Unlike poles attract each other. There is magnetic force of attraction between the opposite poles. South- North poles attract each other.
Mono poles cannot exist.
From the given statements, the magnetic poles are described by:
A north pole must exist with a south pole.
Two south poles placed near each other will repel each other.
A north pole and a south pole placed near each other will attract each other.
Answer:
b) R/4 (There seems to an error in mentioning the multiple choices of this question, please see below explanation of correct calculations for this question.)
Explanation:
dimension of the conductor before melting is l, r
reistivity is p
R=(p*l)/(pie*r2)
after reforming length is reduced to L=l/4
volume in both the cases will be same
i.e. pie * r^2 * l =pie * R^2 * L
r^2 * l = R^2 * (1/2)l
due to this radius will become R=sqrt(2) * r
now new reistance is given by Rx=(p * L)/(pie * R^2)
i.e. Rx=(p * l/2)/(pie * r^2 * 2)
after simplification RX=((p * l)/(pie * r^2))/4
i.e. Rx=R/4
Answer:
(a) I_A=1/12ML²
(b) I_B=1/3ML²
Explanation:
We know that the moment of inertia of a rod of mass M and lenght L about its center is 1/12ML².
(a) If the rod is bent exactly at its center, the distance from every point of the rod to the axis doesn't change. Since the moment of inertia depends on the distance of every mass to this axis, the moment of inertia remains the same. In other words, I_A=1/12ML².
(b) The two ends and the point where the two segments meet form an isorrectangle triangle. So the distance between the ends d can be calculated using the Pythagorean Theorem:
Next, the point where the two segments meet, the midpoint of the line connecting the two ends of the rod, and an end of the rod form another rectangle triangle, so we can calculate the distance between the two axis x using Pythagorean Theorem again:
Finally, using the Parallel Axis Theorem, we calculate I_B:
Answer:
Explanation:
We know that,
Neptune is 4.5×10^9 km from the sun
And given that,
Earth is 1.5×10^8km from sun
Then,
Let P be the orbital period and
Let a be the semi-major axis
Using Keplers third law
Then, the relation between the orbital period and the semi major axis is
P² ∝ a³
Then,
P² = ka³
P²/a³ = k
So,
P(earth)²/a(earth)³ = P(neptune)² / a(neptune)³
Period of earth P(earth) =1year
Semi major axis of earth is
a(earth) = 1.5×10^8km
The semi major axis of Neptune is
a (Neptune) = 4.5×10^9km
So,
P(E)²/a(E)³ = P(N)² / a(N)³
1² / (1.5×10^8)³ = P(N)² / (4.5×10^9)³
Cross multiply
P(N)² = (4.5×10^9)³ / (1.5×10^8)³
P(N)² = 27000
P(N) =√27000
P(N) = 164.32years
The period of Neptune is 164.32years
Felipe was enjoying the sunny day at the beach. He told his friend Carl that he was really enjoying the warm feeling that he was getting as he sat in the Sun. Carl explained that the electromagnetic radiation was responsible for this warm feeling. The electromagnetic spectrum which was responsible for making Felipe feel warm is
<u>Infrared rays</u>
Explanation:
- Infrared radiation (IR), or infrared light, is a type of radiant energy that's invisible to human eyes but that we can feel as heat.
- All objects in the universe emit some level of IR radiation, but two of the most obvious sources are the sun and fire.
- Infrared radiation has a longer wavelength and lower frequency than visible light. Too much exposure can damage your eyes and skin. On a global scale, trapped infrared radiation contributes to global warming.
- Most warm objects in our everyday experiences emit infrared, and half of the energy produced by the Sun is also infrared.
- The primary source of infrared radiation is heat or thermal radiation. This is the radiation produced by the motion of atoms and molecules in an object.
