Physics Important Class 12 Practical Viva

What does Ohm's law state?

The current that flows through most conductors is directly proportional to the voltage applied, provided all physical conditions and temperatures remain constant.

What is the formula for Ohm's law?

Ohm's law is given by the formula: V = IR, where I is current, V is voltage, and R is resistance.

What is specific resistance?

The resistance offered per unit length and unit cross-sectional area when a known amount of voltage is applied.

What is the SI unit of potential difference?

The SI unit of potential difference is volt.

In which unit is current measured?

The unit of electric current is Ampere.

What is the unit of electrical resistance?

The unit of electrical resistance is Ohms.

Does resistance depend on temperature?

Yes, resistance depends on temperature; as temperature increases, resistance also increases.

What is electrical conductivity?

It is the measure of the ability of the material to allow electric current to pass through it.

Define a rheostat.

A rheostat is a two-terminal electrical device whose resistance can be changed to adjust the current flowing through a circuit.

Does resistance depend on the dimensions of the conductor?

Yes, resistance depends on the dimensions of the conductor.

What is the difference between potential difference and emf?

Potential difference is the work done in displacing a unit charge from one point to another; emf is the potential difference among the terminals of a cell when no current is extracted.

Why are connecting wires thick and covered with cotton thread?

Thick copper wires possess negligible resistance, and covering them with cotton helps avoid short-circuiting.

What is the SI unit of resistivity?

Ohm-metre or Ω m is the SI unit of resistivity.

What wire material is used in a rheostat?

Constantan or manganin is the material used in a rheostat.

How can a galvanometer be converted into a voltmeter?

By linking a high resistance in series.

How can a galvanometer be converted into an ammeter?

By linking a low resistance in parallel.

What happens when a voltmeter is linked in series in a circuit?

A voltmeter is used for measuring the potential difference across two points; it has high resistance, thus drastically reducing current.

What is superconductivity?

In specific materials, the resistance completely vanishes below a distinct temperature.

What is a metre bridge?

A slide wire bridge, an instrument used to find unknown resistance of a conductor, working on the principle of Wheatstone bridge.

What is Wheatstone bridge?

A Wheatstone bridge is used in measuring unknown electrical resistance by balancing the two legs of the bridge circuit.

What is Ohmic resistance?

Ohmic resistance is the resistance that obeys Ohm's law.

What is non-ohmic resistance?

Non-ohmic resistance is the resistance that does not obey Ohm's law.

What are two examples of non-ohmic resistance?

Vacuum tube diodes and transistors.

What are three examples of ohmic resistance?

Metallic resistance like silver, aluminum, and copper.

How is an ammeter connected to a circuit?

An ammeter is usually joined in series in the electric circuit.

When is a potentiometer preferred over a voltmeter?

For measuring e.m.f accurately, as it does not take electric current from the cell.

What is the principle of a potentiometer?

The potential dropped along a section of a wire of uniform area carrying a stable electric current is directly proportional to the wire's length.

What is a cell’s e.m.f?

The highest possible potential difference along a cell’s terminals in an open electric circuit.

What does terminal voltage refer to?

Terminal voltage is the potential difference across a cell's terminals when electric current is being drawn from it.

What is a primary cell?

A primary cell is a type of cell that cannot be recharged.

What is a secondary cell?

A secondary cell is a type of cell that can be recharged.

Which type of cells are used in automobiles?

Secondary cells are commonly used in automobiles.

What is total internal reflection?

When light rays travel from a denser medium to a rarer medium and reflect entirely within the denser medium.