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The band of seven colours formed on a white screen, when a beam of white light is passed through a glass prism is called spectrum of white light. A glass prism is used to produce a spectrum.

A. deep under the crust of earth 

Focus of an earthquake is located deep under the ground. Focus is the point inside the crust where the pressure is released. The point on the earth’s surface above the focus is called the epicenter.

C. West Bengal 

The states in India where earthquakes are most likely to occur are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kutch, Rajasthan and the Indo – Gangetic Plane.

(c) they may attract or repel depending on the type of charges they carry 

The outermost layer of the earth is fragmented. Each fragment is called a plate. These plates are in continual motion. When two plates collide head on, they push each other up and form mountains. The Himalayas and other great mountain ranges were created by this process.

D. focus of the earthquake 

Focus of an earthquake is located deep under the ground. Focus is the point inside the crust where the pressure is released. The point on the earth’s surface above the focus is called the epicenter.

The outermost layer of the earth is fragmented. Each fragment is called a plate. These plates are in continual motion. When they brush past one another, or a plate goes under another due to collision they cause disturbance. This disturbance in the earth’s crust shows up as an earthquake on the surface of the earth.

(c) earthquakes

The induced magnetic field will be in the form of concentric circles in the plane of paper.

The outer most layer of the earth is not in one piece. It is fragmented. Each frament is called a earth’s plate.

By using a magnetic compass, that shows deflection.

The power of an earthquake is expressed in terms of a magnitude on ricter scale.

An electromagnet is a device used to generate a magnetic field with the help of an electric current. 

Under the influence of electric current, all atoms are reoriented to start pointing in the same direction. All these individual magnetic fields together create a strong magnetic field. As the current flow increases, this degree of reorientation also increases, resulting in a stronger magnetic field. 

Once all the particles are reoriented perfectly in the same direction, increasing current flow will not affect the magnetic field produced. At this point, the magnet is said to be saturated.

(i) Maximum: When the direction of current is perpendicular to the direction of the magnetic field the force on wire is maximum. 

(ii) Minimum: When the direction of current is parallel to the direction of the magnetic field the force on wire is minimum.

The underground water comes in contact with 'hot spots' present in the earth's crust and stream is generated. This energy possessed by the hot water below the earth is called Geothermal energy.

It can be used to produce electricity.

Because the strength of magnetic field produced by the cable is quite weak

The decrease in deflection of the magnetic compass needle clearly shows that the magnetic field decreases as we move away from the current-carrying conductor.

Direction of current is from right to left as electron beam enters from left to right and magnetic field is into the page. So, according to Fleming’s left hand rule, force is perpendicular to the flow of current and in its left side. So, electron beam deflects towards bottom of the page.

(i) No induced current will be produced in the loop since the constant current flowing in the straight wire produces a constant magnetic field. Hence no induced current is produced in the loop.
(ii) Since current in the straight wire is changing, the magnetic flux associated with the loop will change and hence induced current will be produced in it.
Applying Fleming's Right Hand Rule, the current flowing in the loop will be in clockwise direction.

A magnetic field does not exert any force on a charge moving parallel or antiparallel to the field direction. Since they are travelling in the direction of the magnetic field, there will be no force acting on them. Hence their paths will remain the same after entering the magnetic field.

(a) We can connect the galvanometer to any one of the sources using a key in the circuit. If the galvanometer shows definite deflection in a given direction, the source taken is d.c. source. If the given source is a.c. source, the average deflection shown by the galvanometer will be zero.
(b) We can also connect the electroplating equipment to any one of the sources using a key in the circuit. If electroplating takes place, the source used is d.c. source. In case of AC source, since the direction of current changes in direction periodically and alternatively, there is no definite shifting of the ions of the electrolyte and hence no electroplating takes place.

At every point of current carrying circular loop, the concentric circles representing the magnetic field around it would become larger and larger as we move away from the wire because the magnetic field becomes weaker at a larger distance.

The divergence of magnetic field lines near the ends of a current carrying straight solenoid indicates fall in strength of magnetic field near and beyond the ends of the solenoid.

Strength of the magnetic field falls as distance increases. This is indicated by the decrease in degree of closeness of the lines of field.

(i) Energy can be converted from one form to another.

(ii) Energy in the usable form is dissipated to the surroundings in less usable form.

(iii) Non-renewable source of energy is consumed and cannot be used again.

(i) Yes (ii) No 

A beam of moving electrons constitutes electric current but neutrons are neutral, so no current and hence no magnetic field.

Fuse is connected in series in the circuit.

A magnetic field is a field which is present around magnet and has magnetic properties. So, to produce magnetic field a magnet is surely needed. But we have learnt from the Oersted's experiment that whenever a current is passed through a conductor, a magnetic field is produced around it. 

The current carrying conductor behaves like a magnet. And a magnetic field is produced around it. The magnetic field produced depends on the magnitude of the current and the length or number of loop of current. The direction of the produced magnetic field from a current carrying conductor is given by Right-Hand Thumb Rule.

Electricity is as dangerous as it is useful, in dealing with electricity or electric device one must be very careful. We use electricity in our household and daily life, here are some precautions we should do to prevent any kind of loss: 

1. Avoid water at all times when working with electricity. Never touch or try repairing any electrical equipment or circuits with wet hands. 

2. Always use appropriate insulated rubber gloves and goggles while working on any branch circuit or any other electrical circuit. 

3. Always wear rubber slippers/shoes while handling electricity. 

4. Do not touch anything without complete knowledge. This may cause severe damage. 

5. Never use any electrical device with broken cords, damaged insulation or broken plugs.

True.

Red colour wires are used for live wire; Black colour wires are used for neutral, and green/blue are used for earth wire.

Current flowing through wire I = 8 A
Magnetic field B = 0.15 T
θ = 30°
∴ Force acting on current carrying wire
F = I/B sinθ
Here l = 1 m, then force acting on unit length
F = \(\frac{F}{l}\) = 8 × 0.15 × sin30°
F = 8 × 0.15 × \(\frac{1}{2}\)
F = 0.6 N/m

It can deflect the path of the charged particle.

The drifting of free electrons of a conductor in a definite direction causes the current to flow through it. When such conductor is placed in a uniform magnetic field, each drifted electron of a conductor experience a magnetic force. This force is collectively experience by a conductor as a whole. Hence a current carrying conductor kept in a magnetic field experience a force. The direction of magnetic force depends on 

(i) direction of current through the conductor, and 

(ii) direction of magnetic field.

False.

The electric current which always flows in the same direction is called Direct current, and the electric current which changes its polarity after same intervals of time is called alternating current.

The answer is (b) directly below the wire

By applying right hand thumb rule we can find that direction of magnetic field is from North to South below the wire.

Magnetic field at the centre of the coil will be zero.

Side of square coil = 10 cm
∴ Area of coil A = (10)² = 100cm² = 10^-2 m²
Current flowing I = 12 A
Number of turns in coil N = 20
Magnetic field B = 0.80 T
Angle θ = 30°
Torque acting on coil τ = NIABsinθ
τ = 20 × 10^-2 × 12 × 0.80 × sin 30°
τ = 20 × 12 × 0.80 × \(\frac{1}{2}\) × 10^-2
τ = 0.96 N-m

(A) Ability to retain magnetism when current is removed. 

Correct option (A) Move the magnet faster. 

Explanation:

On moving the magnet faster, the change in net magnetic field associated with the solenoid will be more and hence more e.m.f. will be induced.

Reasons:

(i) Bonus - It should be included because it is compensation paid to employees.

(ii) Addition to stock - It should also be included because it is an investment, a final expenditure.

(iii) Purchase of a Taxi by Taxi Driver - It should be included because it is final expenditure on investment.

Correct option  (B) Anti-ciockwise current will be induced in coil Q, as seen by eye. 

Explanation:

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.

Precautions:

(i) Transfer of payments should not be includes as there is no value addition in the economy.

(ii) Capital gains from sale of old goods should not be included.

(iii) Commission etc of brokers on sale of old goods should be included as these are reward for rendering factor services.

(iv) Transaction in financial assets should not be included.

Precautions of Product Method:

1. Avoid double counting.

2. Production for self consumption should be included.

3. Sale of second hand goods is not to be included.

4. Production from illegal activities is not to be included.

5. Value of services rendered by housewives/family members is not to be included.

Detailed Answer:

Precautions:

(i) Include the value of final product only.

(ii) Sale of second hand goods is not included as these are already accounted for during the year they were produced.

(iii) Include value of own account production in total output.

(iv) Imputed value of owner occupied house should be included.

(v) Value of intermediate goods is not included in the estimation of value added as, the value of intermediate goods is reflected in the value of final goods.

(c) Both electric and magnetic field
When an charged particle is moving with uniform speed produces both electric field and magnetic field.

The counting of the value of commodity more than once is called Double Counting. This leads to overestimation of the value of goods and services produced. Thus, the importance of avoiding double counting lies in avoiding overestimating the value of domestic product.

For example, a farmer produces one ton of wheat and sells it for Rs.400 in the market to a flour mill. The flour mill sells it for Rs.600 to the baker. The baker sells to the bread shopkeeper for Rs.800. The shopkeeper sells the entire bread to the final consumers for Rs.900. Thus,

Value of Output = Rs.400 + Rs.600 + Rs.800 + Rs.900= Rs.2700

In fact, the value of the wheat is counted four times, the value of services of the miller thrice, and the value of services by the baker twice. In other words, the value of wheat and value of services of the miller and of the baker have been counted more than once. The counting of the value of commodity more than once is called Double Counting.

To avoid the problem of double counting two methods are used:

(i) Final Output Method, and

(ii) Value Added Method.

(i) Final Output Method: According to this method, the value of intermediate goods is not considered. Only the value of final goods and services is considered. In the above example, the value of final goods, i.e., Bread is Rs.900.

(ii) Value Added Method: Another method to avoid the problem of double counting is to estimate the total value added at each stage of production. In the above example, the value added at each stage of production is Rs.400 + Rs.200 + Rs.200 + Rs.100 = Rs.900

The counting of the value of commodity more than once is called Double Counting. This leads to overestimation of the value of goods and services produced. Thus, the importance of avoiding double counting lies in avoiding overestimating the value of domestic product.

For example, a farmer produces one ton of wheat and sells it for Rs.400 in the market to a flour mill. The flour mill sells it for Rs.600 to the baker. The baker sells to the bread shopkeeper for Rs.800. The shopkeeper sells the entire bread to the final consumers for Rs.900. Thus,

Value of Output = Rs.400 + Rs.600 + Rs.800 + Rs.900= Rs.2700

In fact, the value of the wheat is counted four times, the value of services of the miller thrice, and the value of services by the baker twice. In other words, the value of wheat and value of services of the miller and of the baker have been counted more than once. The counting of the value of commodity more than once is called Double Counting.

To avoid the problem of double counting two methods are used:

(i) Final Output Method, and

(ii) Value Added Method.

(i) Final Output Method: According to this method, the value of intermediate goods is not considered. Only the value of final goods and services is considered. In the above example, the value of final goods, i.e., Bread is Rs.900.

(ii) Value Added Method: Another method to avoid the problem of double counting is to estimate the total value added at each stage of production. In the above example, the value added at each stage of production is Rs.400 + Rs.200 + Rs.200 + Rs.100 = Rs.900

The counting of the value of commodity more than once is called Double Counting. This leads to overestimation of the value of goods and services produced. Thus, the importance of avoiding double counting lies in avoiding overestimating the value of domestic product.

For example, a farmer produces one ton of wheat and sells it for Rs.400 in the market to a flour mill. The flour mill sells it for Rs.600 to the baker. The baker sells to the bread shopkeeper for Rs.800. The shopkeeper sells the entire bread to the final consumers for Rs.900. Thus,

Value of Output = Rs.400 + Rs.600 + Rs.800 + Rs.900= Rs.2700

In fact, the value of the wheat is counted four times, the value of services of the miller thrice, and the value of services by the baker twice. In other words, the value of wheat and value of services of the miller and of the baker have been counted more than once. The counting of the value of commodity more than once is called Double Counting.

To avoid the problem of double counting two methods are used:

(i) Final Output Method, and

(ii) Value Added Method.

(i) Final Output Method: According to this method, the value of intermediate goods is not considered. Only the value of final goods and services is considered. In the above example, the value of final goods, i.e., Bread is Rs.900.

(ii) Value Added Method: Another method to avoid the problem of double counting is to estimate the total value added at each stage of production. In the above example, the value added at each stage of production is Rs.400 + Rs.200 + Rs.200 + Rs.100 = Rs.900

1. In solenoid the magnetic field lines are nearly parallel while outside bar magnet they are curved.

2. Outside solenoid, magnetic field is nearly zero while in bar magnet it is along its length.

(a) According to right hand rule, the direction of magnetic moment will be perpendicular to plane of paper inwards.
(b) (i) When θ = 90°, then
τ_max = NIABsin90°
τ_max = NIAB
(ii) When θ = 0°
τ_min = 0

(d) ₃Li⁷
Maximum force will be imposed on ₃Li⁷