What is the main reason that some places on the Earth are warmer than others?
A The Sun is closer to some places than others.
B The Sun stays above the horizon 24 hours a day in some places.
C The rays of the Sun are more direct at some places and more slanting at others.
D Some places experience warm seasons because of underground heat.
An electric current passes through a straight wire. Magnetic compasses are placed at the points X and Y.
A Their needles will not deflect.
B Only one of the needles will deflect.
C The needles will deflect in the same direction.
D The needles will deflect in the opposite directions.
Ans 1: (Master Answer)
The correct answer is D
Current carrying wire produces magnetic field, but direction of magnetic field on the given points X and Y are different.
This is found by right hand thumb rule. So magnetic compasses on X and Yexperience magnetic force of same magnitude but in opposite directions. Hence, the needles will deflect in opposite directions.
Three closed similar coils P, Q and R are placed such that their planes are parallel. In the coil P and R, current of same magnitude flows as shown in the figure. Coils Q and R are static while coil P is moved with a uniform speed towards Q, then
A Clockwise current will be induced in coil Q, as seen by eye
B Anti-clockwise current will be induced in coil Q, as seen by eye.
C No current will flow in coil Q
D Current induced in coil Q will be equal to P and R, but in opposite direction, hence net current in Q will be zero.
Ans 1: (Master Answer)
The correct answer is B
Coil P is moved with a uniform speed towards Q while R is static. Due to the current in P, magnetic field is from right to left. When P is moved towards Q, magnetic lines passing through Q (from right to left) will increase, i.e., magnetic flux passing through Q will increase. Therefore, current will be induced in Q. The induced current will have such a direction that it gives a magnetic field opposite to that passing through Q due to current in P. Thus, anticlockwise current will be induced in coil Q, opposite to the direction of current in coil P.
Study the given food web and answer the
(A) How many animals are carnivores?
(B) How many animals are omnivores?
Why D option is correct not option A