directly proportional

(adjective)

If one variable is always the product of the other and a constant, the two are said to be directly proportional.

Related Terms

  • constant

Examples of directly proportional in the following topics:

  • Direct Variation

    • When two variables change proportionally, or are directly proportional, to each other, they are said to be in direct variation.
    • This can also be called directly proportional.
    • Thus we can say that cost varies directly as the value of toothbrushes.
  • Current and Voltage Measurements in Circuits

    • The electrical current is directly proportional to the voltage applied and inversely related to the resistance in a circuit.
    • According to Ohm's law, The electrical current I, or movement of charge, that flows through most substances is directly proportional to the voltage V applied to it.
    • Resistance is inversely proportional to current.
  • Henry's Law

    • Henry's law states that the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas.
    • Henry's law states that at a constant temperature, the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
    • The practical description for the law is that the solubility (i.e., equilibrium) of a gas in a liquid is directly proportional to the partial pressure of that gas.
    • The amount of oxygen that dissolves into the bloodstream is directly proportional to the partial pressure of oxygen in alveolar air. 
    • Henry's law states that when a gas is in contact with the surface of a liquid, the amount of the gas which will go into solution is proportional to the partial pressure of that gas.
  • Hooke's Law

    • Hooke's law of elasticity is an approximation that states that the extension of a spring is directly proportional to the load applied to it.
    • It states: the extension of a spring is in direct proportion with the load applied to it .
    • In simple terms, Hooke's law says that stress is directly proportional to strain.
    • The extension of the spring is linearly proportional to the force.
  • Charles' and Gay-Lussac's Law: Temperature and Volume

    • Charles' and Gay-Lussac's Law states that at constant pressure, temperature and volume are directly proportional.
    • This law states that at constant pressure, the volume of a given mass of an ideal gas increases or decreases by the same factor as its temperature (in Kelvin); in other words, temperature and volume are directly proportional.
  • Direct and Inverse Variation

    • The two variables may be considered directly proportional.
    • Thus we can say that the cost varies directly as the value of toothbrushes.
    • For example, if $x$ and $y$ are inversely proportional, if $x$ is doubled, then $y$ is halved.
    • As an example, the time taken for a journey is inversely proportional to the speed of travel.
    • An inversely proportional relationship between two variables is represented graphically by a hyperbola.
  • Equations of State

    • Boyle's law states that pressure P and volume V of a given mass of confined gas are inversely proportional:
    • while Charles' law states that volume of a gas is proportional to the absolute temperature T of the gas at constant pressure
    • where C is a constant which is directly proportional to the amount of gas, n (representing the number of moles).
  • Combined Variation

    • The two variables may be considered directly proportional.
    • For example, if x and y are inversely proportional, if x is doubled, then y is halved.
    • In this example, z varies directly as x and inversely as y.
    • In the above equation, P varies directly with n and T, and inversely with V.
    • A constant amount of gas will exert pressure that varies directly with temperature.
  • Confidence Interval for a Population Proportion

    • How do you know you are dealing with a proportion problem?
    • p' = the estimated proportion of successes (p' is a point estimate for p, the true proportion)
    • In the error bound formula, the sample proportions p' and q' are estimates of the unknown population proportions p and q.
    • The estimated proportions p' and q' are used because p and q are not known. p' and q' are calculated from the data. p' is the estimated proportion of successes. q' is the estimated proportion of failures.
    • p' = 0.842 is the sample proportion; this is the point estimate of the population proportion.
  • Proportion

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