Electric Current MCQs Quiz | Class 10
This quiz covers important Multiple Choice Questions (MCQs) on Electric Current for Class X Science (Code 086), Unit IV: Effects of Current. Topics included are: Definition, direction, and conventional current. Test your understanding, then submit to see your score and download a detailed answer PDF.
Understanding Electric Current: A Quick Revision
Electric current is a fundamental concept in physics and plays a crucial role in modern technology. This section provides a concise overview of its definition, direction, and the idea of conventional current.
1. Definition of Electric Current
Electric current is defined as the rate of flow of electric charge through a conductor. When charges flow, they constitute an electric current. In metallic conductors, these charges are free electrons.
- Formula: Electric Current (I) = Charge (Q) / Time (t)
- SI Unit: The SI unit of electric current is the Ampere (A). One Ampere is defined as one Coulomb of charge flowing per second (1 A = 1 C/s).
- Charge: The SI unit of electric charge is the Coulomb (C). One Coulomb is approximately equivalent to the charge contained in 6 x 1018 electrons.
2. Direction of Electric Current
There are two perspectives on the direction of electric current:
- Conventional Current: Historically, when electricity was first studied, it was assumed that current flowed from the positive terminal to the negative terminal of a battery or power source. This direction is still widely used in circuit diagrams and is known as conventional current. It flows from a point of higher potential to a point of lower potential.
- Electron Flow: In reality, in metallic conductors, it is the negatively charged electrons that move. Electrons are repelled by the negative terminal and attracted to the positive terminal. Therefore, the direction of electron flow is from the negative terminal to the positive terminal, which is opposite to the direction of conventional current.
Despite this difference, conventional current remains the standard convention used in electrical engineering and physics to describe current flow.
3. Charge Carriers and Materials
The type of charge carriers varies depending on the material:
| Material Type | Primary Charge Carriers | Examples |
|---|---|---|
| Conductors | Free electrons | Copper, Aluminum, Silver |
| Electrolytes | Positive and negative ions | Salt water, Molten salts |
| Semiconductors | Electrons and holes | Silicon, Germanium |
Insulators, such as plastic and wood, have very few free charge carriers, which is why they do not conduct electricity easily.
Quick Revision Points
- Electric current is the flow of electric charge.
- Formula: I = Q/t.
- SI Unit of current is Ampere (A).
- SI Unit of charge is Coulomb (C).
- Conventional current flows from positive to negative.
- Electron flow is from negative to positive.
- Ammeters are used to measure current and are always connected in series.
Practice Questions
- What device is used to measure electric current in a circuit?
- If 10 C of charge passes through a point in a conductor in 2 seconds, what is the current flowing?
- How does an increase in resistance affect the current flowing through a circuit, assuming voltage remains constant?
- Name two good electrical conductors and two good electrical insulators.
- Why are safety fuses connected in series with the live wire in household circuits?
Content created and reviewed by the CBSE Quiz Editorial Team based on the latest NCERT textbooks and CBSE syllabus. Our goal is to help students practice concepts clearly, confidently, and exam-ready through well-structured MCQs and revision content.