Question: The power factor in a single phase circuit is <em>cosΦ = P / VI,</em> where P is the power read by a wattmeter, V is the voltage read by voltmeter and I is the current read by an ammeter. All the three instruments have a limiting error of ±1%. The power factor of the circuits can be known if only one meter i.e an electrodynamometer type power factor having a limiting error ±1% used. The preferred method is to use single instrument like a power factor rather than using 3 instruments because the error with using wattmeter, voltmeter and ammeter is

MCQ: The power factor in a single phase circuit is <em>cosΦ = P / VI,</em> where P is the power read by a wattmeter, V is the voltage read by voltmeter and I is the current read by an ammeter. All the three instruments have a limiting error of ±1%. The power factor of the circuits can be known if only one meter i.e an electrodynamometer type power factor having a limiting error ±1% used. The preferred method is to use single instrument like a power factor rather than using 3 instruments because the error with using wattmeter, voltmeter and ammeter is

• A. ±2%
• B. ±3%
• C. ±1%
• D. -1%