CBSE Class 12 (Science) Current Electricity — practice questions
95 free MCQs with worked solutions. Tap any question for the answer + explanation, or practice them all in the app.
Practice CBSE Class 12 (Science) Current Electricity in the app →An electric current is constituted by:Materials that carry current when a field is applied are:Ohm's law states that V is proportional to:Doubling the length of a conductor makes its resistance:Halving the cross-section area of a conductor makes resistance:The resistance inside a cell itself is called its:Resistance is inversely proportional to the conductor's:The average time between electron collisions is called:The drift velocity of electrons points:Drift velocity is small compared with the electrons':Internal resistance of a cell may be neglected when it is:Compared with electrolytic cells, dry cells have internal resistance that is:Two cells joined can be replaced by one cell of equivalent:How many rules did Kirchhoff give for circuit analysis?Kirchhoff's junction rule for currents I1, I2 into a junction gives:The quantity denoted by sigma, the inverse of resistivity, is:Resistance depends on the material and on the conductor's:If two identical slabs are joined end to end, the combined resistance is:Ohm's law was stated in the year:Ohm's law says the potential difference V equals:In the relation V equals RI, the constant R is called the:In the relation R equals rho l over A, the constant rho is the:Resistivity depends on the conductor's:The reciprocal of resistivity is called:Current per unit area normal to the current is called:The average time between electron collisions is called the:The average velocity of electrons under a field is called the:The surprising feature of drift velocity is that it is independent of:The drift velocity per unit electric field is called:The resistivity of a metallic conductor depends on its:The symbol alpha stands for the temperature coefficient of:The dimension of the temperature coefficient alpha is:Two resistors are in series if they share:Resistors are in parallel if one end of all of them is:Kirchhoff's junction rule concerns the sum of:At a junction, the current entering equals the current:The Wheatstone bridge is made up of how many resistors?In a Wheatstone bridge, the source is connected across the:Which device detects the current in a Wheatstone bridge?The resistance offered by the cell itself is called:Which scientist discovered in 1828 that potential difference across a conductor is proportional to current?In the SI system, electric current is measured in which unit?A steady current through an area is best described as which ratio?A charge of 120 C passes through a wire in 40 s. What is the steady current?Currents in the nerves of the body are typically of what order?An average lightning stroke carries a current of what order of magnitude?What is the net current in a metal wire when no electric field is applied?What do cells and batteries do in a conductor?With no field applied, an electron leaves a collision with an ion. Its new direction is what?How does the drift velocity of conduction electrons relate to the electric field direction?Drift speed is given by vd = I/(neA). What does n stand for?Why does current start almost instantly on closing a circuit?Why do electrons reach a steady average drift speed?How can a large current flow with a drift speed of mm per second?Between successive collisions, how do electron paths look when an electric field is present?Mobility of a charge carrier is defined as the drift velocity per unit what?A uniform conductor has cross-section A, electron density n and drift velocity vd. What is the current?A wire has its length doubled with the same cross-section and material. What happens to its resistance?A wire is stretched to twice its length at constant volume. Resistance becomes how many times?The resistivity of a given metal wire changes mainly when which quantity changes?Metals have resistivities lying in which range?Which lists materials by increasing resistivity?How does the resistivity of a semiconductor change as temperature rises?For a metallic conductor, the temperature coefficient of resistivity has which sign?Why does the resistivity of a metal rise with temperature?At fixed electron density, doubling the average time between collisions does what to resistivity?Why is nichrome used in standard resistors?Nichrome is an alloy of which metals?An appliance on a 230 V supply draws 2 A. What power does it use?A 100 ohm heater coil is connected across 200 V. What power is dissipated?Why does a conductor carrying steady current heat up?In a cell and resistor circuit, what supplies the heat power?The emf of a cell equals the potential difference between its terminals under which condition?What kind of quantity is the emf of a cell, despite its name?A 12 V cell with 1 ohm internal resistance drives a 5 ohm resistor. What is the terminal voltage?A 6 V cell has internal resistance 0.5 ohm. What is the maximum current it could supply?How does the internal resistance of dry cells compare with common electrolytic cells?Two 1.5 V cells have the positive terminal of one joined to the negative of the other. What is the combined emTwo cells in series have internal resistances 0.2 ohm and 0.3 ohm. What is the equivalent internal resistance?Three identical 2 V, 3 ohm cells are in parallel. Equivalent internal resistance?Kirchhoff's junction rule expresses the conservation of which quantity?The sum of potential changes around a closed loop is zero. This follows from conservation of what?At a junction, 3 A and 2 A enter and one wire carries away 1.5 A. What current leaves through the remaining wiA single loop has a 12 V battery with 2 ohm and 4 ohm resistors in series. What is the current?A circuit solution gives a negative current. What does it mean?Why are Kirchhoff's rules needed for some circuits?A Wheatstone bridge with four resistors gives zero galvanometer deflection. This is called what?A balanced bridge has P = 10 ohm, Q = 20 ohm, R = 30 ohm with P/Q = R/S. What is S?At the balance point of a Wheatstone bridge, what is the current through the galvanometer?A Wheatstone bridge is practically used to do what?Which device does not give the same current when the voltage sign is reversed?For GaAs, which feature of the V and I relation breaks Ohm's law?Which statement about Ohm's law is correct?A platinum wire is 5 ohm at the ice point and 5.23 ohm at the steam point. What is its temperature coefficientA steady current of 1.6 A flows in a wire. About how many electrons cross a section each second?