Probes of CRO

Q. The input impedance of a CRO is equivalent to a $1M\Omega$ resistance in parallel with a $45pF$ capacitance. It is used with a compensated 10 to 1 attenuation probe. The effective input capacitance at the probe tip is

1. 4.5 pF
2. 5 pF
3. 45 pF
4. 450 pF

Q. An oscilloscope input impedance consists of $1M\Omega$ resistance connected in parallel with a $100pF$ capacitor. A compensted $20:1$ attenuator is obtained by connecting a parallel combination of ___.

1. $19M\Omega and\frac{100}{19}pF$
2. $200M\Omega and\frac{100}{20}pF$
3. $19M\Omega and1900pF$
4. $19M\Omega and2000pF$

Q. A CRO probe has an impedance of $500k\Omega$ in parallel with a capacitance of $10\mu F$. The probe is used to measure the voltage between P and Q as shown in figure. The measured voltage will be

1. 3.53 V
2. 4.37 V
3. 4.54 V
4. 5.00 V

Q. A signal is applied at the input terminals of the circuit shown below. To attenuate the input signal by a factor of 10. The values of $R_1,C_1$ respectively are

1. $9M\Omega ,3.33pF$
2. $9M\Omega ,270pF$
3. $\frac{1}{9}M\Omega ,270pF$
4. $\frac{1}{9}M\Omega ,3.33pF$

Q. An oscilloscope is powered from $230V$ mains having a nominal frequency of nearly $50Hz.$ The triggering mode of the oscilloscope is set to LINE. A square wave from a function generator is fed to the Y input and a stable display (properly triggered) is obtained when the frequency of the function generator is $297Hz.$ The actual frequency of the power supply is

1. $50Hz$
2. $49.5Hz$
3. $49.0Hz$
4. $48.5Hz$