Current and Resistance
A 12 V battery is connected across a single 4 Ω resistor. This is the current through the resistor.
What is 3 A?
Two 4 Ω resistors are connected in series. This is the equivalent resistance of the pair.
What is 8 Ω?
A current of 2 A flows through a device when 12 V is applied across it. This is the power dissipated.
What is 24 W?
At a circuit junction, two wires carry currents of 3 A and 2 A into the junction. Only one other wire is connected. This is the current flowing through it, and its direction.
What is 5 A flowing out of the junction?
Once a capacitor in a DC circuit is fully charged, this is the current flowing through it.
What is zero?
A wire's length is doubled while its cross-sectional area and material stay the same. This is what happens to its resistance.
What is it doubles?
Two 4 Ω resistors are connected in parallel. This is the equivalent resistance of the pair.
What is 2 Ω?
When the voltage across a fixed resistor is doubled, the power it dissipates changes by this factor.
What is 4 (it quadruples)?
A 9 V battery is connected in a single loop with three resistors in series: 1 Ω, 2 Ω, and 6 Ω. This is the current in the loop.
What is 1 A?
A 5 μF capacitor is fully charged across a 10 V battery. This is the charge stored on it
What is 50 μC?
Two wires of the same material and length have circular cross-sections, but wire A's diameter is twice wire B's. This is the ratio of wire A's resistance to wire B's resistance.
What is 1 to 4?
Two identical bulbs are wired in series with a battery. A third identical bulb is then added in parallel with one of them. The brightness of the remaining series bulb does this.
What is it gets brighter?
A 4 Ω resistor and an 8 Ω resistor are connected in parallel across the same battery. This is the ratio of the power dissipated by the 4 Ω resistor to that of the 8 Ω resistor.
What is 2 to 1?
A real battery is short-circuited, connected directly across its own terminals with effectively zero external resistance. This is its terminal voltage during the short.
What is approximately zero?
A parallel-plate capacitor is connected to a battery and reaches steady state. The plate separation is then halved while the battery stays connected. The energy stored in the capacitor does this
A copper wire's temperature rises from 20 °C to 120 °C. Using α ≈ 4 × 10⁻³ /°C, this is the percent increase in its resistance.
What is 40%?
A 24 V battery is connected to a 2 Ω resistor in series with a parallel combination of a 6 Ω and a 3 Ω resistor. This is the current through the 6 Ω resistor.
What is 2 A?
A 60 W and a 100 W incandescent bulb (both rated for 120 V) are mistakenly wired in series across a single 120 V outlet. This is which bulb glows more brightly.
What is the 60 W bulb?
A 12 V battery and a 6 V battery are wired in a single loop with their positive terminals facing each other (so they oppose each other), in series with a single 3 Ω resistor. This is the current in the circuit.
What is 2A?
A 4 μF and a 2 μF capacitor are connected in parallel and charged to 12 V by a battery. This is the total energy stored in the combination.
What is 432 μJ?
A wire of resistance R is melted down and recast (same total volume) into a new wire whose length is three times the original. This is the resistance of the new wire.
What is 9R?
Three identical bulbs A, B, and C (each of resistance R) are wired so that bulb A is in series with a parallel combination of B and C, then connected to a battery. This is the ratio of bulb A's brightness to bulb B's brightness.
What is 4 to 1?
A real battery has emf 12 V and internal resistance 0.5 Ω. This is the maximum power that can be delivered to an external resistor (over all possible external resistances).
What is 72 W?
A battery with emf 20 V and internal resistance 2 Ω is connected to an external circuit consisting of a 4 Ω resistor in parallel with a 12 Ω resistor. This is the power dissipated as heat inside the battery
What is 32W?
A 100 μF capacitor charged to 20 V is allowed to discharge through a 50 kΩ resistor. This is the voltage across the capacitor 10 seconds later.
What is ~2.7 V?