The condition under which a microwave oven heats up a food item containing water molecules most efficiently is:
| 1. | the frequency of microwaves has no relation with the natural frequency of water molecules. |
| 2. | microwaves are heatwaves, so always produce heating. |
| 3. | infrared waves produce heating in a microwave oven. |
| 4. | the frequency of the microwaves must match the resonant frequency of the water molecules. |
| 1. | \(1000~\text{J}\) | 2. | zero |
| 3. | \(-2000~\text{J}\) | 4. | \(2000~\text{J}\) |
| 1. | twice per revolution. |
| 2. | four times per revolution. |
| 3. | six times per revolution. |
| 4. | once per revolution. |
The velocity of a projectile at the initial point \(A\) is \(2\hat i+3\hat j~\text{m/s}.\) Its velocity (in m/s) at the point \(B\) is:
| 1. | \(-2\hat i+3\hat j~\) | 2. | \(2\hat i-3\hat j~\) |
| 3. | \(2\hat i+3\hat j~\) | 4. | \(-2\hat i-3\hat j~\) |
The following four wires are made of the same material. Which of these will have the largest extension when the same tension is applied?
| 1. | length = \(100~\text{cm},\) diameter = \(1~\text{mm}\) |
| 2. | length = \(200~\text{cm},\) diameter = \(2~\text{mm}\) |
| 3. | length = \(300~\text{cm},\) diameter = \(3~\text{mm}\) |
| 4. | length = \(50~\text{cm},\) diameter = \(0.5~\text{mm}\) |
1. \(4~\Omega\)
2. \(8~\Omega\)
3. \(16~\Omega\)
4. \(2~\Omega\)
| 1. | Wien’s displacement Law |
| 2. | Kirchhoff’s Law |
| 3. | Newton’s Law of cooling |
| 4. | Stefan’s Law |
1. solid sphere
2. hollow sphere
3. disc
4. ring
A bar magnet of length \(l\) and magnetic dipole moment \(M\) is bent in the form of an arc as shown in the figure. The new magnetic dipole moment will be:
| 1. | \(\dfrac{3M}{\pi}\) | 2. | \(\dfrac{2M}{l\pi}\) |
| 3. | \(\dfrac{M}{ 2}\) | 4. | \(M\) |
A rod \(PQ\) of mass \(M\) and length \(L\) is hinged at end \(P\). The rod is kept horizontal by a massless string tied to point \(Q\) as shown in the figure. When the string is cut, the initial angular acceleration of the rod is:
| 1. | \(\dfrac{g}{L}\) | 2. | \(\dfrac{2g}{L}\) |
| 3. | \(\dfrac{2g}{3L}\) | 4. | \(\dfrac{3g}{2L}\) |
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