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Quizzes > Science

Ohms Law Test: Practice Voltage, Current, and Resistance

Quick physics quiz on ohm's law circuits. Instant results and explanations.

Editorial: Review CompletedCreated By: Matthew HibberdUpdated Aug 23, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art illustration for electricity and Ohms Law quiz on a golden yellow background

Use this quiz to practice Ohm's law and build speed solving for voltage, current, resistance, and power in simple circuits. If you want more practice, try our voltage current resistance quiz, work through kvl and kcl practice problems, or check fundamentals with an electrical circuits quiz. Get instant feedback as you go.

What is the SI unit of electrical resistance?
Ampere (A)
Volt (V)
Ohm (?)
Watt (W)
Electrical resistance is measured in ohms, symbolized by ?, defined by the ratio of voltage to current. It follows directly from Ohm's law: R = V/I. This unit is part of the SI system and is named after Georg Simon Ohm. For more details, see .
Which of the following is the SI unit of electric current?
Watt (W)
Ampere (A)
Volt (V)
Coulomb (C)
Electric current is measured in amperes, defined as one coulomb of charge passing a point per second. It is one of the seven base SI units. The ampere is named after André-Marie Ampère. Learn more at .
What is the SI unit of electric potential difference (voltage)?
Volt (V)
Joule (J)
Ampere (A)
Ohm (?)
Voltage, or electric potential difference, is measured in volts which represent one joule of energy per coulomb of charge. It's a derived SI unit named after Alessandro Volta. Voltage drives current through a circuit according to Ohm's law. See for details.
Which equation correctly represents Ohm's law?
V = I ÷ R
R = V + I
V = I × R
I = V + R
Ohm's law states that the voltage across a resistor is the product of the current through it and its resistance: V = I × R. This linear relationship holds for many conductive materials under constant temperature. Deviations occur in non-ohmic devices. More at .
How do you calculate the total resistance for resistors connected in series?
Subtract the smaller from the larger
Use reciprocal sum: 1/R_total = 1/R1 + 1/R2 + ...
Add the resistances: R_total = R1 + R2 + ...
Multiply the resistances
In a series circuit, the total resistance is simply the sum of each individual resistor because the current passes through each one sequentially. This adds to the overall opposition to current flow. Parallel calculations use reciprocals instead. See .
Two identical resistors are connected in parallel. What is the equivalent resistance compared to one resistor?
Half the resistance
The same resistance
Double the resistance
One quarter the resistance
For two equal resistors R in parallel, the equivalent is R/2 because 1/R_total = 1/R + 1/R = 2/R. Combining them gives a lower resistance. Parallel circuits divide current among paths. More at .
If the voltage across a resistor remains constant, what happens to the current when the resistance increases?
The current decreases
The current stays the same
The current becomes infinite
The current increases
Ohm's law (I = V/R) shows that for a constant voltage, increasing R causes I to decrease. This inverse relationship explains why higher resistance limits current flow. It's fundamental to circuit design. See .
What happens to the resistance of a uniform conductor if its length is doubled while its cross-sectional area remains constant?
It doubles
It remains the same
It quadruples
It halves
Resistance is directly proportional to length (R = ?L/A). Doubling L while keeping area A constant doubles the resistance. Material resistivity and geometry determine resistance. More at .
Which expression gives the electrical power dissipated by a resistor?
P = V × I
P = V² ÷ R
P = I² × R
All of the above
Electrical power in a resistor can be expressed in multiple ways: P = VI, and substituting Ohm's law gives P = I²R or P = V²/R. All formulas are equivalent under Ohm's law. See .
A 10 ? resistor has a voltage of 20 V across it. What is the current flowing through it?
10 A
200 A
2 A
0.5 A
Using Ohm's law I = V/R, substituting V = 20 V and R = 10 ? yields I = 20/10 = 2 A. This straightforward calculation follows basic circuit rules. More at .
What does Kirchhoff's Voltage Law state?
Voltage is constant across series elements
Power generated equals power dissipated
The algebraic sum of all voltages around any closed loop is zero
The algebraic sum of currents at a junction is zero
Kirchhoff's Voltage Law (KVL) states that the sum of potential differences around a closed loop equals zero, reflecting energy conservation. Each rise and drop in voltage along the loop cancels out. Read more at .
What is the principle of Kirchhoff's Current Law?
Total resistance in a circuit is constant
Voltage around a loop sums to zero
Power in equals power out
The sum of currents entering a junction equals the sum leaving it
Kirchhoff's Current Law (KCL) states that at any electrical junction, the sum of currents flowing into the node equals the sum flowing out, reflecting charge conservation. It underpins nodal analysis. See .
Two resistors, 4 ? and 6 ?, are in series, and that combination is in parallel with an 8 ? resistor. What is the total resistance?
18 ?
7.11 ?
4.44 ?
2.67 ?
First, series R = 4 + 6 = 10 ?. Then parallel with 8 ?: 1/R_total = 1/10 + 1/8 = 0.225, so R_total ? 4.44 ?. This combines series and parallel rules. See .
How does the resistivity of most metals change with temperature?
It increases
It oscillates
It decreases
It remains constant
For most metals, resistivity increases as temperature rises because lattice vibrations scatter electrons more. This positive temperature coefficient is common in conductors. Some materials like semiconductors behave differently. More at .
A device shows a straight-line voltage vs. current graph through the origin. What does this behavior indicate?
It is capacitive
It behaves as an ohmic conductor
It is inductive
It is a semiconductor diode
A linear V - I characteristic through the origin signifies a constant resistance device, known as an ohmic conductor. Capacitors and inductors show frequency-dependent impedance, and diodes have nonlinear curves. More at .
Which of these devices is non-ohmic and does not have a constant resistance?
A superconductor below critical temperature
A filament lamp
A fixed resistor
A metal wire at constant temperature
Filament lamps change resistance with temperature: as the filament heats, its resistance rises, so V - I curve is nonlinear. Fixed resistors and metals at constant temperature remain ohmic. Superconductors drop to zero resistance below critical temperature. Read more at .
A Thevenin equivalent circuit is best described as what combination?
A voltage source in parallel with a single resistor
A current source in parallel with a single resistor
A single voltage source in series with a single resistor
A current source in series with a single resistor
Thévenin's theorem states any linear network can be reduced to a voltage source (Vth) in series with a resistance (Rth) as seen from two terminals. This simplifies analysis when connecting loads. More at .
What does the Norton equivalent circuit consist of?
A current source in series with a resistor
A voltage source in series with a resistor
A current source in parallel with a resistor
A voltage source in parallel with a resistor
Norton's theorem states that any linear network can be reduced to a current source (IN) in parallel with a resistance (RN) as seen from two terminals. It's often used interchangeably with Thévenin's form. Details at .
In a delta-to-wye (? - Y) transformation, the resistor connected to node A in the wye network is given by which expression?
R_AB + R_AC - R_BC
(R_AB × R_AC) ÷ (R_AB + R_BC + R_AC)
R_AB ÷ (R_BC + R_AC)
(R_BC × R_AC) ÷ (R_AB + R_BC)
In ? - Y conversion, the resistor R_A in the star network equals the product of the two delta resistances adjacent to node A divided by the sum of all three delta resistances. This formula simplifies complex networks. See .
What is the key principle behind the node-voltage method of circuit analysis?
Applying KCL at circuit nodes to solve for unknown voltages
Applying KVL around closed loops
Balancing power in each branch
Converting all sources to current sources
Node-voltage (nodal) analysis uses Kirchhoff's Current Law at each node to form equations in terms of node voltages. It's efficient for circuits with many elements. More at .
Mesh analysis relies primarily on which law to determine loop currents?
Kirchhoff's Current Law at each node
Kirchhoff's Voltage Law around each mesh
Maximum power transfer theorem
Ohm's law only
Mesh (loop) analysis applies Kirchhoff's Voltage Law to each independent loop, writing equations based on voltage drops and rises. It simplifies multi-loop circuits. Learn more at .
A 12 V battery has an internal resistance of 1 ?. When connected to a 5 ? load, what is the terminal voltage?
7 V
2 V
10 V
12 V
Terminal voltage Vt = E × (R_load / (R_load + r_int)) = 12 × (5/6) = 10 V. The internal resistance causes a voltage drop under load. More at .
Which formula relates resistance (R) to resistivity (?), length (L), and cross-sectional area (A)?
R = ? ÷ (L × A)
R = ? × A ÷ L
R = L ÷ (? × A)
R = ? × L ÷ A
Resistance of a uniform conductor is R = ?L/A, where ? is resistivity, L is length, and A is cross-sectional area. This shows geometry and material properties determine resistance. Details at .
Which safety device protects a circuit by melting its internal element under overcurrent conditions?
Fuse
Ground fault interrupter
Circuit breaker
Voltage regulator
A fuse contains a thin metal strip that melts when current exceeds its rating, interrupting the circuit. Circuit breakers reset mechanically, and GFCIs detect imbalance. Fuses are simple and reliable. Learn more at .
For maximum power transfer from a Thevenin equivalent circuit to a load, what condition must be satisfied?
Load resistance equals Thevenin resistance
Load resistance is half Thevenin resistance
Load resistance is zero
Load resistance is twice Thevenin resistance
The maximum power transfer theorem states that a load receives maximum power when its resistance equals the Thevenin equivalent resistance of the source network. This balances voltage drop and current. More at .
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Study Outcomes

  1. Apply Ohm's Law -

    Use the relationship between voltage, current, and resistance to solve for unknown circuit values with confidence.

  2. Calculate Circuit Parameters -

    Determine the correct voltage, current, or resistance in single-loop circuits using fundamental equations.

  3. Interpret Electrical Units -

    Recognize and convert volts, amperes, and ohms to ensure accurate calculations in any electrical problem.

  4. Analyze Circuit Configurations -

    Examine simple series and parallel circuits to predict total resistance and current distribution.

  5. Identify Formula Usage -

    Select the appropriate circuit laws and apply them to various quiz scenarios involving voltage and current.

  6. Reinforce Electrical Fundamentals -

    Consolidate your understanding of basic circuit principles through targeted electricity quiz questions.

Cheat Sheet

  1. Ohm's Law Fundamentals -

    Ohm's Law establishes the relationship V = I × R, where voltage (V), current (I), and resistance (R) are interdependent. For example, a 9 V source driving 3 Ω of resistance yields a current of 3 A (I = V/R). This law is foundational in circuits and is covered extensively in MIT OpenCourseWare.

  2. Series vs. Parallel Circuit Behavior -

    In series circuits, current remains constant while voltages divide, whereas in parallel circuits, voltage is constant and current divides among branches. You can calculate total resistance in series (R_total = R1 + R2 + …) and in parallel (1/R_total = 1/R1 + 1/R2 + …) as per Georgia State University's HyperPhysics resource. Understanding these behaviors helps you tackle complex circuit problems quickly.

  3. Units and Measurement Tools -

    Accurate measurement of volts, amps, and ohms requires a quality multimeter calibrated to IEEE standards. Always start with the highest range to prevent instrument damage, then adjust to read the precise value. Good measurement habits are emphasized by Fluke's electrical training modules.

  4. Power Calculations -

    Circuit power (P) can be found using P = V × I, and by combining Ohm's Law you get P = I² × R or P = V² / R. For instance, a 2 A current through a 5 Ω resistor dissipates 20 W of heat. The IEEE Power & Energy Society highlights these formulas in its fundamentals guides.

  5. Resistor Color Codes & Tolerance -

    Memorizing resistor color codes is made easy with mnemonics like "Bad Boys Race Our Young Girls But Violet Goes Wasting" to recall 0 - 9. The colored bands indicate significant figures, multiplier, and tolerance, critical for selecting proper resistor values. This method is widely taught in electronics labs at universities such as Stanford and Cornell.

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