CBSE Class 7 Science Chapter 10 Electric Current and its Effects — 20 MCQs with Answers

NCERT Class 7 Science introduces standard symbols for drawing electric circuits — cell, battery, switch (open and closed), bulb, wire, resistor, and ammeter. These symbols are universal and help students communicate circuit designs clearly. CBSE papers often show a circuit diagram and ask students to identify components or predict behaviour. Familiarity with symbols saves time and avoids confusion during exams. Questions may also ask students to draw a circuit for a given verbal description, testing both recall and application.

When current flows through a conductor, it generates heat — this is the heating effect. The amount of heat depends on the resistance of the wire and the square of the current (Joule's law). Appliances like electric irons, toasters, and geysers exploit this effect. A fuse is a safety device: a thin wire of tin-lead alloy with low melting point that melts and breaks the circuit if current exceeds a safe limit, preventing fires. CBSE questions often ask about fuse wire material, why it is thin, and its role in household circuits. Understanding that high resistance and narrow cross-section produce more heat is key.

A current-carrying conductor produces a magnetic field around it — this is the magnetic effect of electric current, discovered by Hans Christian Oersted in 1820. When a wire is wound into a coil and current passes through it, the coil behaves like a magnet; inserting an iron core inside the coil strengthens this effect, creating an electromagnet. Electromagnets are temporary magnets whose strength can be controlled by changing current or the number of turns in the coil. They are used in electric bells, cranes for lifting scrap metal, and loudspeakers. CBSE questions test the factors affecting electromagnet strength and the direction of the magnetic field.

An electric bell uses the magnetic effect of current to produce sound. When the circuit is closed by pressing the switch, current flows through an electromagnet. The electromagnet attracts an iron strip (armature) which is attached to a hammer. The hammer strikes the gong, producing sound. Simultaneously, the armature moves away from a contact screw, breaking the circuit. The electromagnet loses magnetism, the armature springs back, reconnects the circuit, and the cycle repeats rapidly, creating a continuous ringing. CBSE questions often ask about the sequence of events, the role of the electromagnet, or what happens if the electromagnet is replaced by a permanent magnet.

CBSE Class 7 Science papers increasingly include application-based questions where students must apply concepts to new situations, and diagram-based questions where a circuit or device diagram is shown and students identify components or predict outcomes. These questions test deeper understanding beyond rote memorisation. For Electric Current and its Effects, expect diagrams of circuits with switches, bulbs, and ammeters, or cross-sections of an electric bell. Practice reading diagrams carefully: identify the direction of current flow, count the number of turns in a coil, or spot whether a switch is open or closed. Such questions carry high marks and reward careful observation.

Many Class 7 students lose easy marks in MCQs by misreading the question, confusing heating and magnetic effects, or selecting the first option that sounds correct without reading all four. A frequent error is mixing up symbols — for example, confusing the symbol for a cell with a battery, or a resistor with a wire. Another mistake is not understanding the word 'temporary' in electromagnet questions, leading to wrong answers about permanent magnets. In assertion-reason questions, students often mark both statements true without checking if the reason actually explains the assertion. Careful reading, eliminating obviously wrong options first, and reviewing NCERT diagrams before the exam can prevent these pitfalls.

Multiple-choice questions in CBSE Class 7 Science carry 1 mark each and are usually the first section of the paper. Speed and accuracy matter. Start by reading the question stem carefully — underline keywords like 'not', 'except', 'increases', or 'best'. Eliminate obviously incorrect options first; even removing one wrong choice improves your odds from 25% to 33%. For assertion-reason questions, evaluate the assertion and reason separately, then check if the reason explains the assertion. If a diagram is given, study it for 10-15 seconds before reading options. Never leave an MCQ blank — there is no negative marking in CBSE Class 7 term exams. If unsure, make an educated guess and move on. Reserve 2-3 minutes at the end to review flagged questions. Avoid changing answers unless you spot a clear mistake; your first instinct is often correct.

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