Explanation

• Heat has the same units as work, energy, and enthalpy

Standard Units

• Joule (J): Standard SI unit for heat, work, and energy.
• Calorie (cal): Metric unit for heat and food energy
• Newton-meter (N·m): Mechanical unit equivalent to a Joule.

Explanation

In a conductor, the electric field inside the conductor (in the material itself) must be zero. So:

The inner surface of the shell must carry a charge that exactly cancels the field from the charge inside the cavity.

Since there's a –3 C charge at the center, the inner surface must have a charge of +3C to neutralize the field inside the conductor.

Explanation

We are told:

• A copper penny is heated to 100 °C.

• Its diameter increases by 0.17%.

• We are to find the percentage increase in the area of one of its circular faces.

Let’s denote:

• Original diameter: $D$
  

• Increased diameter: $D' = D + Delta D = D (1 + 0.0017)$

• Area of a circle: $\mathrm{<br>}$

• New area:

  A′=π(D′)^2​/4=(D(1+0.0017))^2/4π​=A⋅(1+0.0017)^2

Use binomial expansion (for small x):

(1+x)^2≈1+2xwhen x is small

Here, $x=0.0017$, so:

(1+0.0017)^2≈1+2(0.0017)=1+0.0034=1.0034

Thus, the area increases by:

0.34%​

Explanation

As a raindrop falls:

• Initially, it accelerates due to gravity.

• As its speed increases, air resistance (a drag force) also increases.

• Eventually, a point is reached where the upward air resistance equals the downward gravitational force.

• At this point, net force = 0, so acceleration stops, and the raindrop continues falling at a constant speed.

This constant speed is called terminal velocity.

Explanation

We are given:

• $A=B\cdot C$

• Dimensions:

  • [A]=L/M​

  • [C]=L/T​

We want to find $[B]$.

Step 1: Solve for
$\mathrm{<br>}$B:

B=A/C​

Step 2: Plug in dimensions:

$$<br>$$[C]​

=L​/M/L/T

​​=L​/M​⋅T/L​=T/M​

Explanation

The unit of magnetic flux density is Wb m⁻² (weber per square meter).

It is commonly referred to as a tesla (T), which quantifies the strength of the magnetic field.

Explanation

A dipole in an electric field behaves in two ways:

• In a uniform electric field:

The two equal and opposite forces cancel each other out.

So, the net force on the dipole is zero.

But a torque is produced that tends to align the dipole moment parallel to the electric field.

• In a non-uniform electric field:

The dipole does experience a net force, and that force is generally not simply parallel to the field.

So the correct answer remains:

(D) None of these — because in a uniform electric field, the net force on a dipole is zero.

Option (C) would be correct only if we were talking about torque direction or net force in a non-uniform field.