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A magnetic compass needle is placed in the plane of paper near point A. In which plane should a straight current-carrying conductor be placed so that it passes through A and there is no change in the deflection of the compass? Under what condition is the deflection maximum and why?

In the plane of the paper itself. The axis of the compass is vertical and the field due to the conductor is also vertical. It could result in a... View Article

The most important safety method used for protecting home appliances from short-circuiting or overloading is (a) earthing (b) use of fuse (c) use of stabilizers (d) use of electric meter

b) use of fuse The primary use of an electric fuse is to protect electrical equipment from excessive current and to prevent short circuits or... View Article

To convert an AC generator into DC generator (a) split-ring type commutator must be used (b) slip rings and brushes must be used (c) a stronger magnetic field has to be used (d) a rectangular wire loop has to be used

a) split-ring type commutator must be used A split-ring commutator makes the current change direction every alternate half-rotation, whereas a... View Article

The strength of the magnetic field inside a long current carrying straight solenoid is (a) more at the ends than at the centre (b) minimum in the middle (c) same at all points (d) found to increase from one end to the other

(c) same at all points Inside the solenoid magnetic field lines are straight. This indicates strong magnetic field. Hence, magnetic field is... View Article

A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in Figure. The direction of the magnetic field at a point will be North to South (a) directly above the wire (b) directly below the wire (c) at a point located in the plane of the paper, on the north side of the wire (d) at a point located in the plane of the paper, on the south side of the wire

b) directly below the wire The Fleming's right-hand rule shows the direction of induced current when a conductor moves in a magnetic field. The... View Article

Choose the incorrect statement (a) Fleming’s right-hand rule is a simple rule to know the direction of induced current (b) The right-hand thumb rule is used to find the direction of magnetic fields due to current-carrying conductors (c) The difference between the direct and alternating currents is that the direct current always flows in one direction, whereas the alternating current reverses its direction periodically (d) In India, the AC changes direction after every 1/50 second

d) In India the AC changes direction after every 1/50 second Fleming's right-hand rule shows the direction of induced current when a conductor... View Article

In the arrangement shown in the figure there are two coils wound on a non-conducting cylindrical rod. Initially, the key is not inserted. Then the key is inserted and later removed. Then (a) the deflection in the galvanometer remains zero throughout (b) there is a momentary deflection in the galvanometer but it dies out shortly and there is no effect when the key is removed (c) there are momentary galvanometer deflections that die out shortly; the deflections are in the same direction (d) there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

d) there are momentary galvanometer deflections that die out shortly, the deflections are in opposite directions In the figure, two coils... View Article

Commercial electric motors do not use (a) an electromagnet to rotate the armature (b) effectively large number of turns of conducting wire in the current-carrying coil (c) a permanent magnet to rotate the armature (d) a soft iron core on which the coil is wound

c) a permanent magnet to rotate the armature In an electric motor, a rectangular coil is placed in between the magnetic field and when current... View Article

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in the figure. In the field an electron and a proton move as shown. The electron and the proton experience (a) forces both pointing into the plane of paper (b) forces both pointing out of the plane of paper (c) forces pointing into the plane of paper and out of the plane of paper, respectively (d) force pointing opposite and along the direction of the uniform magnetic field respectively

(a) forces both pointing into the plane of the paper For the given figure, the proton and electron are moving in opposite directions to each... View Article

For a current in a long straight solenoid N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is (a) The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid (b) The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil (c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet (d) The N- and S-poles exchange position when the direction of current through the solenoid is reversed

(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet. The... View Article

A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is ON. The current as seen from points A and B (in the plane of the paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to (a) A (b) B (c) A if the current is small, and B if the current is large (d) B if the current is small and A if the current is large

(a) A The direction of the magnetic field will be from south to north pole. Point A is showing North Pole because field lines are pointing... View Article

If the key in the arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are (a) concentric circles (b) elliptical in shape (c) straight lines parallel to each other (d) concentric circles near the point O but of elliptical shapes as we go away from it

c) Straight lines parallel to each other If the key in the arrangement is taken out (the circuit is made open) then there will be no... View Article

Choose the incorrect statement from the following regarding magnetic lines of the field (a) The direction of the magnetic field at a point is taken to be the direction in which the north pole of a magnetic compass needle points (b) Magnetic field lines are closed curves (c) If magnetic field lines are parallel and equidistant, they represent zero-field strength (d) The relative strength of the magnetic field is shown by the degree of closeness of the field lines

(c) If magnetic field lines are parallel and equidistant, they represent zero-field strength They have uniform magnetic field and doesn’t... View Article

Write how the following seeds are dispersed. (a) Seeds with wings. (b) Small and light seeds. (c) Seeds with spines/hooks.

(a) Seeds with wings are dispersed by wind. Due to the winged structure, the wind can easily blow off these seeds to different locations.... View Article

The male and female gametes fuse to form a _(a) during the process of _(b)__. This grows into an _(c)__ which is enclosed within a seed. After fertilisation the ovules develop into _(d)__ and the ovary develops into a _(e)____ .

The male and female gametes fuse to form an (a) zygote during the process of (b) fertilization. This grows into a (c) embryo which is enclosed... View Article

Coconut is a large and heavy fruit. How is it adapted for dispersal by water?

Even though coconut is large and heavy, it contains an outer fibrous coat which has the ability to float on water. It can drift in water bodies... View Article

When you keep food items like bread and fruits outside for a long time especially during the rainy season, you will observe a cottony growth on them. (a) What is this growth called? (b) How does growth take place?

(a) The growth is called a mould. It is formed by fungus.They are fast-growing fungi and have a cottony appearance (b) The growth takes place... View Article

One morning as Paheli strolled in her garden she noticed many small plants which were not there a week ago. She wondered where they had come from as nobody had planted them there. Explain the reason for the growth of these plants.

Sometimes, plants grow without a human support. New plants are produced from seeds or from vegetative parts. The seeds developed in the parent... View Article

Boojho had the following parts of a rose plant – a leaf, roots, a branch, a flower, a bud and pollen grains. Which of them can be used to grow a new rose plant?

Branch, pollen grains. Rose flower is a bisexual flower. Rose plant can be grown by vegetative propagation as well as sexual... View Article

Pick the odd one out from the following on the basis of mode of reproduction and give reason for it. (sugarcane, potato, rice, rose)

Rice Vegetative propagation is an asexual method of plant reproduction that occurs in its leaves, roots and stem. This can occur through... View Article

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