**Answer:**

The illumination on the book before the lamp is moved is 9 times the illumination after the lamp is moved.

**Explanation:**

The distance of the book before the lamp is moved,

The distance of the book after the lamp is moved,

Illumination can be given by the formula,

Illumination before the lamp is moved,

Illumination after the lamp is moved,

The illumination on the book before the lamp is moved is 9 times the illumination after the lamp is moved.

**Answer:**

**Explanation:**

The resistance of a wire is given by:

where

is the resistivity of the material

L is the length of the wire

A is the cross-sectional area of the wire

1) The first wire has length L and cross-sectional area A. So, its resistance is:

2) The second wire has length twice the first one: 2L, and same thickness, A. So its resistance is

3) The third wire has length L (as the first one), but twice cross sectional area, 2A. So, its resistance is

By comparing the three expressions, we find

So, this is the ranking of the wire from most current (least resistance) to least current (most resistance).

**Answer:**

The correct option is (B).

**Explanation:**

The electric potential is the amount of work energy needed to move a unit of electric charge from a reference point to the specific point in an electric field. The electric potential due to a point charge is given by :

Where

k is the electrostatic constant

Q is the electric charge

r is the distance from the charge

**So, a positive electric charge in a region of changing electric potential will move in the direction of increasing potential.**

**Answer:**

v = 12.12 m/s

**Explanation:**

**Given that,**

Radius of the curvature, r = 30 m

**To find,**

The car's speed at the bottom of the dip.

**Solution,**

Let mg is the true weight of the passenger. When it is moving in the circular path, the centripetal force act on it. It is given by :

The normal reaction of the passenger is given by :

N = 1.5 mg

Let v is the car's speed at the bottom of the dip. It can be calculated as:

**v = 12.12 m/s**

**So, the speed of the car at the bottom of the dip is 12.12 m/s. Hence, this is the required solution.**

**Explanation:**

-body temp: when cold, erector muscle contract, hair raise, vasoconstriction occurs, sweat production reduces, muscle shiver to enhance metabolism, and thyroid gland secret more thyroxine to enhance metabolism

-water potential balance: when we are thirsty, pituitary gland secret more ADH, kidney tubules become more permeable to water, so more water re-absorbed, less urine produced, retaining more water.