Vidaara.orgClass 8 · Mathematics
CodeVID-M8-WS
Chemical Effects of Electric Current — Practice Worksheet
Name: ____________________
Roll No.: __________
Date: ____________
General Instructions
- All questions are compulsory.
- Choose the correct option (A, B, C or D) for each question.
- The answer key is at the end — try the paper first!
Section A — Multiple Choice (1 mark each)
25 × 1 = 25 marks
1.
A liquid that conducts electricity is called a/an:
- A.Insulator
- B.Electrolyte
- C.Conductor metal
- D.Vacuum
2.
Liquids conduct electricity because they contain free:
- A.Atoms only
- B.Ions
- C.Electrons in metal
- D.Molecules of gas
3.
In a conduction tester, a liquid conducts if the:
- A.Bulb does not glow
- B.Bulb glows
- C.Battery melts
- D.Wire breaks
4.
Which of these does NOT conduct electricity?
- A.Salt solution
- B.Dilute acid
- C.Distilled water
- D.Lemon juice
5.
An LED is used instead of a bulb because it can detect a:
- A.Strong current only
- B.Very weak current
- C.Magnetic field
- D.High voltage only
6.
The decomposition of a conducting liquid by an electric current is called:
- A.Reflection
- B.Electrolysis
- C.Evaporation
- D.Distillation
7.
The electrode connected to the positive terminal of the battery is the:
- A.Cathode
- B.Anode
- C.Resistor
- D.Filament
8.
In the electrolysis of water, the gas released at the cathode is:
- A.Oxygen
- B.Hydrogen
- C.Carbon dioxide
- D.Nitrogen
9.
In the electrolysis of water, the gas released at the anode is:
- A.Hydrogen
- B.Oxygen
- C.Helium
- D.Chlorine
10.
When copper sulphate solution is electrolysed, copper is deposited on the:
- A.Anode
- B.Cathode
- C.Wire
- D.Battery
11.
Electroplating is the process of depositing a thin layer of one ______ over another object.
- A.Gas
- B.Metal
- C.Liquid
- D.Plastic
12.
In electroplating, the object to be coated is connected as the:
- A.Anode
- B.Cathode
- C.Battery
- D.Switch
13.
Tin is electroplated onto iron to make food cans because tin:
- A.Rusts quickly
- B.Does not rust easily and is non-toxic
- C.Is poisonous
- D.Is magnetic
14.
Jewellery is often electroplated with gold or silver to:
- A.Make it heavier
- B.Give an attractive, valuable look cheaply
- C.Make it rust
- D.Conduct electricity
15.
An advantage of electroplating is that it:
- A.Causes rusting
- B.Protects metals from corrosion
- C.Removes shine
- D.Weakens the object
16.
The amount of metal deposited in electrolysis depends on the current and the:
- A.Colour
- B.Time of current flow
- C.Temperature of the room
- D.Size of the wire only
17.
If a larger current is passed for the same time, the metal deposited will be:
- A.Less
- B.More
- C.The same
- D.Zero
18.
If the current flows for a longer time, the metal deposited will be:
- A.Less
- B.More
- C.The same
- D.None
19.
To get a thicker coating in electroplating, one should use:
- A.Smaller current, shorter time
- B.Larger current, longer time
- C.No current
- D.A magnet
20.
This principle lets manufacturers control the ______ of the electroplated coating.
- A.Colour only
- B.Thickness
- C.Smell
- D.Sound
21.
Which of these is NOT an effect of electric current?
- A.Heating effect
- B.Magnetic effect
- C.Chemical effect
- D.Gravitational effect
22.
The chemical effect of current occurs when current passes through a:
- A.Solid metal wire
- B.Conducting liquid
- C.Vacuum
- D.Magnet
23.
A sign of the chemical effect of current in a liquid is:
- A.The wire melting
- B.Gas bubbles at the electrodes
- C.A loud sound
- D.A bright flash only
24.
The heating effect of current is used in:
- A.Electroplating
- B.Electric heaters
- C.A compass
- D.A magnet
25.
Besides electroplating, the chemical effect of current is used industrially to:
- A.Cool metals
- B.Extract and purify metals
- C.Produce sound
- D.Reflect light
Answer Key
Section A — Multiple Choice (1 mark each)
- (B) Electrolyte
- (B) Ions
- (B) Bulb glows
- (C) Distilled water
- (B) Very weak current
- (B) Electrolysis
- (B) Anode
- (B) Hydrogen
- (B) Oxygen
- (B) Cathode
- (B) Metal
- (B) Cathode
- (B) Does not rust easily and is non-toxic
- (B) Give an attractive, valuable look cheaply
- (B) Protects metals from corrosion
- (B) Time of current flow
- (B) More
- (B) More
- (B) Larger current, longer time
- (B) Thickness
- (D) Gravitational effect
- (B) Conducting liquid
- (B) Gas bubbles at the electrodes
- (B) Electric heaters
- (B) Extract and purify metals
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