English Medium Class 10 - CBSE Question Bank Solutions for Science

A silver article generally turns black when kept in the open for a few days. The article when rubbed with toothpaste again starts shining.

1.  Why do silver articles turn black when kept in the open for a few days? Name the phenomenon involved.
2. Name the black substance formed and give its chemical formula.

What happens when zinc granules are treated with dilute solution of H₂SO₄, HCl, HNO₃, NaCl and NaOH Also write the chemical equations if reaction oçcurs.

On adding a drop of barium chloride solution to an aqueous solution of sodium sulphite, white precipitate is obtained :

1. Write a balanced chemical equation for the reaction involved.
2. What other name can be given to this precipitation reaction?
3. On adding dilute hydrochloric acid to the reaction mixture, white precipitate disappears. Why?

You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO₃, ZnCl₂ and water. In which of the above containers, can these solutions be kept?

For a current in a long straight solenoid N- and S-poles are created at the two ends. Among the following statements, the incorrect statement is

A simple motor is made in a school laboratory. A coil of wire is mounted on an axle between the poles of a horseshoe magnet, as illustrated.

In the example above, coil ABCD is horizontal and the battery is connected as shown.

1. For this position, state the direction of the force on the arm AB.
2. Why does the current in the arm BC not contribute to the turning force on the coil?

In the redox reaction:

MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂

A copper wire is held between the poles of a magnet

The current in the wire can be reversed. The pole of the magnet can also be changed over. In how many of the four directions shown can the force act on the wire?

Which of the following pattern correctly describes the magnetic field around a long straight wire carrying current?

State whether the given chemical reaction is a redox reaction or not. Justify your answer.

\[\ce{MnO_2 + 4HCl->MnCl_2 +2H_2O + Cl_2}\]

A reddish brown metal used in electrical wires when powdered and heated strongly turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on this information answer the following questions:

1. Name the metal and the black substance formed.
2. Write balanced chemical equations for the two reactions involved in the above information

State the change in colour observed in following case mentioning the reason:

Copper powder is strongly heated in air.

An alpha particle enters a uniform magnetic field as shown. The direction of force experienced by the alpha particle is ______.

Assertion (A): A current carrying straight conductor experiences a force when placed perpendicular to the direction of magnetic field.

Reason (R): The net charge on a current carrying conductor is always zero.

Two LED bulbs of 10W and 5W are connected in series. If the current flowing through 5W bulb is 0.005A, the current flowing through 10W bulb is ______.

Consider the following combinations of resistors:

1. 
   
2. 
   
3. 
   
4. 
   
   The combinations having equivalent resistance 1 Q is/are ______.

An electric lamp of 100 Ω, a toaster of resistance 50 Ω, and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?

What are the advantages of connecting electrical devices in parallel with the battery instead of connecting them in series?