What formula is used to calculate voltage in a circuit?
The correct answer is A: E = I × R. The formula used to calculate voltage in a circuit is E = I × R, which is Ohm's Law. This fundamental relationship states that voltage (E, in volts) equals current (I, in amperes) multiplied by resistance (R, in ohms).
Ohm's Law is one of the most important principles in electronics and electrical engineering. It describes the relationship between voltage, current, and resistance in a circuit. When you know any two of these values, you can calculate the third. The formula E = I × R means that voltage increases when either current or resistance increases. This law applies to DC circuits and is essential for understanding how circuits work, calculating power consumption, and designing electronic equipment.
Exam Tip
Ohm's Law formula = E = I × R. Remember: Voltage (E) equals Current (I) times Resistance (R). This is the fundamental relationship - memorize it as 'E equals I times R'.
Memory Aid
"**E** = **I** × **R** (think 'EIR' - Easy to Remember: **E**quals **I** times **R**esistance)"
Real-World Application
You're troubleshooting your transceiver. You measure 2 amperes of current flowing through a 50-ohm resistor. Using Ohm's Law (E = I × R), you calculate the voltage: E = 2 × 50 = 100 volts. This helps you understand the power dissipation and verify your circuit is operating correctly.
Key Concepts
Why Other Options Are Wrong
Option B: Incorrect. E = I / R would mean voltage decreases as resistance increases, which is backwards. Voltage increases with resistance when current is constant.
Option C: Incorrect. E = I + R would add current and resistance, which have different units (amperes and ohms) and cannot be directly added.
Option D: Incorrect. E = I - R would subtract resistance from current, which is mathematically invalid due to different units.
题目解析
The correct answer is A: E = I × R. The formula used to calculate voltage in a circuit is E = I × R, which is Ohm's Law. This fundamental relationship states that voltage (E, in volts) equals current (I, in amperes) multiplied by resistance (R, in ohms). Ohm's Law is one of the most important principles in electronics and electrical engineering. It describes the relationship between voltage, current, and resistance in a circuit. When you know any two of these values, you can calculate the third. The formula E = I × R means that voltage increases when either current or resistance increases. This law applies to DC circuits and is essential for understanding how circuits work, calculating power consumption, and designing electronic equipment.
考试技巧
Ohm's Law formula = E = I × R. Remember: Voltage (E) equals Current (I) times Resistance (R). This is the fundamental relationship - memorize it as 'E equals I times R'.
记忆口诀
**E** = **I** × **R** (think 'EIR' - Easy to Remember: **E**quals **I** times **R**esistance)
实际应用示例
You're troubleshooting your transceiver. You measure 2 amperes of current flowing through a 50-ohm resistor. Using Ohm's Law (E = I × R), you calculate the voltage: E = 2 × 50 = 100 volts. This helps you understand the power dissipation and verify your circuit is operating correctly.
错误选项分析
Option B: Incorrect. E = I / R would mean voltage decreases as resistance increases, which is backwards. Voltage increases with resistance when current is constant. Option C: Incorrect. E = I + R would add current and resistance, which have different units (amperes and ohms) and cannot be directly added. Option D: Incorrect. E = I - R would subtract resistance from current, which is mathematically invalid due to different units.
知识点
Ohm's Law, Voltage calculation, E = I × R, Circuit fundamentals
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.