IB_Measurements and Uncertainties

The resistance R of a resistor is determined by measuring the potential difference V across it and the current I in it. The value of R is then calculated using the equation

 $R=\frac{V}{I}$  .
The values measured are V = 1.00 ± 0.05 V and I = 0.50 ± 0.01 A. What is the % uncertainty in the value of R?

• 2.5 %

• 3.0 %

• 7.0 %

• 10.0 %

A quantity x is to be determined from the equation

x = P-Q.

P is measured as 1.27 ± 0.02 m and Q is measured as 0.83 ± 0.01 m.

What is the percentage uncertainty in x to one significant figure?

• 0.4 %

• 2 %

• 3 %

• 7 %

A quantity x is to be determined from the equation

x = P-Q.

P is measured as 1.27 ± 0.02 m and Q is measured as 0.83 ± 0.01 m.

What is the percentage uncertainty in x to one significant figure?

• 0.4 %

• 2 %

• 3 %

• 7 %

The first length measured in a laboratory experiment is 2.5 + 0.1 m and the second length 3.4 + 0.1 m. What is the uncertainty of the sum of the lengths?

• 0.1 m

• 0.2 m

• 0.3 m

• 0.4 m

The first length measured in a laboratory experiment is 2.5 + 0.1 m and the second length 3.4 + 0.1 m. What is the uncertainty of the difference in the lengths?

• 0.1 m

• 0.2 m

• 0.3 m

• 0.4 m

State the order of magnitude of the following: 0.000656

• 10 ^-4

• 10 ^-3

• 10 ^-2

• 10 ^-1

A number rounded to the nearest power of 10 is called:

• Estimation

• Orders of magnitude

• Metric multipliers

• Prefixes

True or False?

Repeating a reading never removes the systematic error.

• True

• False

What could reduce systematic errors?

• averaging a large number of measurements

• careful calibration of measuring instruments

• reducing the sample size

• repeating measurements

The power loss P in a resistor is usually calculated using the formula  $P=\frac{V^2}{R}$  
The percentage uncertainty in the potential difference V is 3 % and the percentage uncertainty in the resistance R is 2 %. What is the percentage uncertainty in P?

• 4 %

• 7 %

• 8 %

• 11 %