Current Electricity MCQs for MDCAT

Correct answer: B. Time base generator

The sawtooth voltage applied across the X-plates of an oscilloscope, which sweeps the electron beam horizontally at a constant rate, is generated by a circuit called the time base generator.

Correct answer: C. 4π x 10-3 T

Using B = μ0nI with n = 300/0.15 = 2000 turns/m and I = 5 A, B = 4π×10⁻⁷ × 2000 × 5 = 4π×10⁻³ T.

Correct answer: D. Resistance

The reciprocal of resistance is conductance, measuring how easily current flows through a conductor.

Correct answer: A. Zero ohm

A resistor with a single black band is known as a zero-ohm resistor. It’s primarily used as a wire link to connect traces on a printed circuit board (PCB). The resistor package allows the same automated pick-and-place machines to place the components on a circuit board. So, the resistance value of a resistor with a single black band is 0 ohms.

Correct answer: A. Zero

In a pure inductor, the voltage and current are out of phase by 90 degrees. This means that when the current is at its maximum (or minimum), the voltage across the inductor is zero, and when the voltage is at its maximum (or minimum), the current through the inductor is zero. As a result, the average power dissipated over a complete cycle is zero.

Correct answer: A. R-L circuit

At high frequencies, the inductive reactance (XL) of the inductor in the RLC series circuit increases significantly. This increase in XL dominates the behavior of the circuit, making it behave more like an R-L circuit where the inductor's impedance is dominant, and the capacitor's impedance is negligible. As a result, at high frequencies, an RLC series circuit behaves more like an R-L circuit.

Correct answer: B. 12 V

Given: Magnetic field strength = B = 0.6 T Length = L = 1m Velocity = v = 20 m/s emf = ε = ? As we know that: emf = vBL = 20 × 0.6 × 1 emf = 12 v

Correct answer: D. Temperature coefficient of resistance

The temperature coefficient of resistance represents how the resistance of a conductor changes with temperature. It is defined as the fractional change in resistance per Kelvin.

Correct answer: C. Lenz’s Law

Lenz's law, in electromagnetism, states that an induced electric current flows in a direction such that the current opposes the change that induced it.

Correct answer: B. 300

To calculate the rate of energy dissipation (power) in an X-ray tube, we use the formula P = IV, where P is the power in watts, I is the current in amperes, and V is the voltage in volts. In this case, the current is given as 5mA, which is equal to 0.005A (since 1A = 1000mA). The voltage is 60kV, which is equal to 60000V (since 1kV = 1000V).Now, substituting the values into the formula: P = 0.005A * 60000V = 300 Watts. Therefore, the correct answer is Option B: 300 watts.The other options are incorrect because:Option A (560): This value does not correspond to the correct calculation.Option C (200): This is too low for the given current and voltage.Option D (800): This is too high and does not match the calculated power.

Correct answer: A. V=W/Q

The potential difference (V) between two points is defined as the work (W) required to move a unit charge (Q) from one point to the other. Mathematically, this is expressed as:V = W/QThis equation shows that the potential difference is directly proportional to the work done and inversely proportional to the charge

Correct answer: B. Ohm's Law

Ohm's Law states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance.