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Name the waves used for echo depth sounding.
Concept: Echo >> Use of Echoes
Two sound waves X and Y have the same amplitude and the same wave pattern but their frequencies are 60 Hz and 120 Hz respectively, then ______.
Concept: Sound Waves

The above picture shows a mother pushing her daughter sitting on a swing. The swing is going through the positions A, B, C where A and C are extreme positions and B is the mean position.
- Which is the right position i.e. at A, B or C, for the mother to give a constant periodic push to the swing every time in the forward direction to increase the amplitude of the swing? (1)
- Name the phenomenon involved in this. (1)
- Explain with this example how this phenomenon helps to increase the amplitude of the swing. (2)
Concept: Resonance (a special case of forced vibrations) >> Examples of Resonance
Which particles are responsible for current in conductors?
Concept: Electrical Power
Concept: Resistance of a System of Resistors >> Resistors in Series
The diagram below shows a cardboard on which iron filings are kept. A wire bent in the form of a loop is seen passing through the cardboard. When current flows through it, the iron filings arrange themselves as shown below.

- State the polarities of the battery at A and B.
- State the effect on the magnetic field if an iron rod is held along the axis of the coil.
- State one way to:
- Change the polarity of the coil.
- Decrease the strength of the magnetic field around the coil.
Concept: Terminal Voltage of a Cell
The circuit depicted in the figure is employed for studying Ohm’s Law. Instead of using a standard resistor, a student opts for a glass tube filled with mercury (tube 1), connected to the circuit through two electrodes, E1 and E2. He records the readings of the ammeter and voltmeter, thereby calculating the resistance. The student repeats the experiment by substituting tube 1 with tube 2, where the same amount of mercury fills tube 2.

Neglecting internal resistance of the cell use (> or < or =) to compare:
- the resistance in both the cases.
- the voltmeter readings in both the cases.
- the specific resistance in both the cases.
Concept: Ohm's Law
To which wire of a cable in a power circuit should the metal case of geyser be connected.
Concept: Earthing
To which wire should the fuse be connected?
Concept: Fuse
According to the old convention, the colour of the earth wire is ______.
Concept: Colour Coding of Wires in a Cable
When does the nucleus of an atom tend to become radioactive?
Concept: Radioactivity
A brass ball is hanging from a stiff cotton thread. Draw a neat labeled diagram showing the forces acting on the brass ball and cotton thread
Concept: Moment (Turning Effect) of a Force or Torque
The distance between two bodies is doubled. How is the magnitude of the gravitational force between them affected?
Concept: Centre of Gravity
A uniform half meter rule balances horizontally on a knife-edge at 29 cm mark when a weight of 20 gf is suspended from one end
1) Draw a diagram of the arrangement
2) What is the weight of the half meter rule?
Concept: Centre of Gravity
How does uniform circular motion differ from uniform linear motion?
Concept: Uniform Circular Motion (UCM)
Give an example of a non-contact force which is always of attractive nature
Concept: Centre of Gravity
How does the magnitude of this non-contact force on the two bodies depend on the distance of separation between them?
Concept: Moment (Turning Effect) of a Force or Torque
An effort is applied on the bigger wheel of a gear having 32 teeth. It is used to turn a wheel of 8 teeth. Where it is used.
Concept: Moment (Turning Effect) of a Force or Torque
On what factor does the position of the center of gravity of a body depend?
Concept: Centre of Gravity
What is the SI unit of the moment of force?
Concept: Moment (Turning Effect) of a Force or Torque
