For a 12 V supply and 3 kΩ resistor, what current flows?
A 4 mA
B 0.25 mA
C 3 mA
D 36 mA
Answer: A. 4 mA. Ohm’s law gives I = V/R = 12 V/3 kΩ = 4 mA.
Combining 2 kΩ and 3 kΩ in series gives what?
A 0.5 kΩ
B 6 kΩ
C 1 kΩ
D 5 kΩ
Answer: D. 5 kΩ. Series resistances add, giving 2 kΩ + 3 kΩ = 5 kΩ.
What equivalent resistance results from connecting 6 Ω and 3 Ω in parallel?
A 2 Ω
B 3 Ω
C 18 Ω
D 9 Ω
Answer: A. 2 Ω. The parallel equivalent is (6 × 3)/(6 + 3) = 2 Ω.
In steady-state ideal DC, a charged capacitor behaves like what?
A Current source
B Short circuit
C Open circuit
D Voltage source
Answer: C. Open circuit. After charging is complete, an ideal capacitor carries no steady DC current.
At steady-state ideal DC, an inductor behaves like what?
A Open circuit
B Current source
C Short circuit
D Voltage source
Answer: C. Short circuit. With constant current, an ideal inductor has zero voltage across it.
With a 10 ms period, what frequency does this periodic signal have?
A 100 Hz
B 10 Hz
C 1000 Hz
D 50 Hz
Answer: A. 100 Hz. Since f = 1/T, a period of 0.010 s gives 100 Hz.
What RMS voltage corresponds to a 100 V sine-wave peak?
A 100 V
B 70.7 V
C 50 V
D 141.4 V
Answer: B. 70.7 V. For a sine wave, RMS voltage is peak voltage divided by √2.
Conventional current flows externally in which direction?
A Negative to positive
B Ground to supply
C Positive to negative
D Either direction
Answer: C. Positive to negative. Conventional current flows from a source’s positive terminal toward its negative terminal through the external circuit.
When forward biased, an ideal diode behaves like what?
A Voltage source
B Current source
C Open switch
D Closed switch
Answer: D. Closed switch. An ideal forward-biased diode is modeled as a closed switch.
To limit Zener current, which added component is required?
A Parallel capacitor
B Series resistor
C Shunt diode
D Current meter
Answer: B. Series resistor. The series resistor limits current and protects the Zener diode.
In which BJT mode does a transistor switch ON?
A Breakdown
B Saturation
C Active region
D Cutoff
Answer: B. Saturation. A switching BJT is driven into saturation for its ON state.
Which BJT region represents its switch-off state?
A Cutoff
B Active region
C Saturation
D Breakdown
Answer: A. Cutoff. In cutoff, the transistor’s collector current is ideally negligible.
Common-emitter amplifiers shift voltage phase by how many degrees?
A 0 degrees
B 270 degrees
C 90 degrees
D 180 degrees
Answer: D. 180 degrees. A common-emitter voltage amplifier inverts its output, producing a 180° phase shift.
When V+ exceeds V−, where should an ideal comparator output move?
A Ground level
B Positive rail
C Zero current
D Negative rail
Answer: B. Positive rail. A comparator drives positive when its non-inverting input is above its inverting input.
How many degrees separate output and input in an inverting op amp?
A 180 degrees
B 270 degrees
C 0 degrees
D 90 degrees
Answer: A. 180 degrees. The minus sign in the inverting gain indicates a 180° phase reversal.
Non-inverting op-amp gain has which sign?
A Negative
B Undefined
C Positive
D Zero
Answer: C. Positive. A non-inverting amplifier preserves the signal polarity, so its gain is positive.
With negative feedback, ideal op-amp input voltages are approximately what?
A Zero
B Opposite
C Equal
D Unrelated
Answer: C. Equal. In linear operation with negative feedback, the input differential voltage approaches zero.
Where is the output taken in a basic voltage divider?
A Supply terminal
B Ground terminal
C Transformer core
D Resistor midpoint
Answer: D. Resistor midpoint. The divider output is taken from the junction between its series resistors.
In a balanced Wheatstone bridge, what current flows through the detector?
A Zero
B Infinite current
C Base current
D Supply current
Answer: A. Zero. At balance, the detector terminals have equal potential, so detector current is zero.
Overcurrent protection is provided by which component?
A Inductor
B Relay
C Capacitor
D Fuse
Answer: D. Fuse. A fuse opens the circuit when current exceeds its rated limit.
As frequency rises, capacitive reactance does what?
A Stays constant
B Becomes zero
C Decreases
D Increases
Answer: C. Decreases. Capacitive reactance is 1/(2πfC), so it decreases as frequency increases.
With frequency increase, inductive reactance does what?
A Becomes zero
B Increases
C Stays constant
D Decreases
Answer: B. Increases. Inductive reactance is 2πfL, so it increases with frequency.
Which filter passes low frequencies and attenuates high ones?
A High-pass filter
B Notch filter
C Band-pass filter
D Low-pass filter
Answer: D. Low-pass filter. A low-pass filter passes frequencies below its cutoff and attenuates higher ones.
Which filter passes high frequencies?
A Low-pass filter
B High-pass filter
C Band-pass filter
D Notch filter
Answer: B. High-pass filter. A high-pass filter attenuates low frequencies and passes higher ones.
How does a step-down transformer change AC voltage?
A Reduces it
B Reverses polarity
C Stops current
D Doubles it
Answer: A. Reduces it. A step-down transformer has fewer secondary turns and produces a lower voltage.