Class 6 to 8 - Physics Coaching Classes & Tuition Centers in Vadodara

The factors affecting density of a substance are its mass, volume, physical state of matter and the ambient temperature.

Density of a substance is directly proportional to its mass. while inversely proportional to its volume and ambient temperature. Density of a substance also varies with the change in its physical state.

Answer:

 When a current carrying conductor is placed in a magnetic field,it experiences a force which produces a torque that rotates the conductor. This is because  any current carrying conductor will produce an electromagnetic field around it and so the magnetic field produced by the conductor will interact with the main magnetic field already present which exerts a force on the conductor. The direction of the force is readily given by Fleming's Left  hand rule 

Suppose the sides of the coil(conductor) are AA' and BB' and the direction of current in the coil is such that the current enters along AA' and leaves along BB'. Let us assume that the coil experiences a torque in a counter clockwise direction when the coil side AA' is under  North pole of the main field. After rotating through half turn, the coil side BB' comes under  North pole.But as the direction of current in BB' is opposite to that of AA',the torque now will be in clockwise direction and as a result no unidirectional torque will be produced to rotate the coil.

Now suppose the direction of current in the coil side BB' is reversed (and automatically in AA' is also reversed),when it comes under  North pole,the torque will again be counterclockwise. And after completion of full turn,the current in coil side AA' will again be reversed  when it comes under  North pole so that a unidirectional torque is produced and the coil continues to rotate  counter clockwise. This automatic reversal  of the current is accomplished by commutator and brush gear and so the DC motor rotates continuously.   

As 1 light year is the distance travelled by light in vacuum in one year therefore distance of quasar from earth is 3× 10^ 9 light years

We know that S.I unit of power lens 1dioptre,D= reciprocal of focal length(f) in metre So, D=1/f or, f=1/D=1/2= 0.5 metre= 50 c.m. So, focal length of this lens is = 50 c.m.

1Horse Power= 746 Watts

Cell is the active source or elements in electric circuit. It's main function is to give power supply to the closed circuit or for which current will flow through the circuit.

Distance of the object from optical centre of the convex lens (u)= 15 c.m. Focal length of the convex lens (v)= 30 c.m. Let's, distance of image formed from optical centre= v c.m. Now, applying lens formula, 1/v - 1/u = 1/f; or, 1/v -1/15= 1/30 or, 1/v= 1/15 - 1/30 or, 1/v= - 1/30 or,v= -30 So, from sign convention formula of lens image will be formed on same side of the object and 30 cm from optical centre. Image nature will be virtual and erect.

Here uniform electric field (E) is parallel to the axis of the cone . So, at any point on the cone surface uniform electric field(E) and area vector (dA) will be perpendicular to each other. So, total flux for the surface of the cone= ( vector E)•(vector dA)= E (dA) cos(theta)= E (dA) cos 90 = 0 Here correct answer is option (d).

Motion is important when force is applied.

Coulomb's law states that: The magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them. In order to obtain both the magnitude and direction of the force on a charge, q 1 at position, experiencing a field due to the presence of another charge, q 2 at position , the full vector form of Coulomb 's law is required.